JP3067937B2 - Method for manufacturing semiconductor light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor light emitting device. More specifically, the present invention relates to a method for manufacturing a short-wavelength semiconductor laser that emits red to orange laser light and a light-emitting diode (LED) in a red to green wavelength band.

[0002]

2. Description of the Related Art In recent years, 630 using AlGaInP as a material has been developed.
-680 nm red semiconductor laser is used as a light source for POS,
It is attracting attention as a light source for high-definition and high-density magneto-optical disks, and is being actively researched and developed. When used for a disk, the stability of the fundamental mode and optical characteristics such as astigmatism are particularly important. Therefore, a refractive index guide type structure that confine light in the oscillation region is desired.

As a conventional 680 nm band refractive index guide type semiconductor laser device, there are known an effective refractive index guide type shown in FIG. 11 and a real refractive index guide type shown in FIG. The semiconductor laser device shown in FIG. 11 has an n- (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P clad layer (having a thickness of 1.100) on an n-GaAs substrate 131 having (100) as a main surface by MOCVD.
5 μm) 133, a non-doped Ga _0.5 In _0.5 P active layer (thickness 0.05 μm) 134, and p- (Al _0.5 Ga _0.5 ) _0.5 In _0.5
P cladding layer (thickness: 1.5 μm) 135 and p-Ga _0.5 In
_{A 0.5P} intermediate layer 136 is grown. Next, after the ridge portion 141 is removed from the surface of the intermediate layer 136 to the middle of the cladding layer 135 by etching, leaving the ridge portion 141 at the center of the element, the n-GaAs current confinement layer 132 is removed from the ridge portion 141.
Grown on both sides of the P-GaAs contact layer
(Thickness: 2 μm) 137 is grown. Finally, the substrate 13
The electrodes 139 and 140 are formed on the back surface of the substrate 1 and the surface of the contact layer 137, respectively. In this semiconductor laser, the current confinement layer 132 restricts the current path to reduce the reactive current, and gives a substantially large mode loss to the higher-order mode of oscillation. Therefore, the higher-order oscillation mode is suppressed, and the fundamental mode oscillation is stably maintained up to a high optical output in the oscillation region 134a.

Further, the semiconductor laser device shown in FIG.
N-GaAs is formed on a p-GaAs substrate 101 having a (100) plane.
A current confinement layer 102 is formed, and a groove 102b extending from the surface of the current confinement layer 102 to the substrate 101 is formed. Next, p- (Al _0.5 Ga _0.5 ) _0.5 In _0.5
P cladding layer (thickness: 1.8 μm) 103 and non-doped Ga
_0.5 In _0.5 P active layer (thickness: 0.05 μm) 104 and n- (Al
_0.5 Ga _0.5 ) _0.5 In _0.5 P cladding layer (1.5 μm thickness) 10
5 and n-Ga _0.5 In _0.5 P contact layer (thickness 1 μm) 10
6 are formed in order (the thickness of each layer is
This is a value within b. ). Finally, the electrodes 10 are provided on the back surface of the substrate 101 and the surface of the contact layer 106, respectively.
9, 110 are formed. In the growth by the MOCVD method, the growth layer generally grows while reflecting the shape of the underlying layer. I have. As a result, a real refractive index guide structure is formed. As a result, the loss in the fundamental mode is reduced, the oscillation threshold is reduced, and the differential efficiency is increased.

[0005]

However, FIG.
In the semiconductor laser device shown in (1), the stability of the fundamental mode depends on the thickness of the cladding layer left on both sides of the ridge 141.
There is a problem that the fundamental mode becomes unstable when the residual thickness d greatly exceeds 0.3 μm due to a variation in etching (the optimal value of the residual thickness d is 0.3 μm). Exists around 2 μm). The same applies to the case where the remaining thickness d differs between the left and right sides of the ridge 141. Also, at the stage of growing the current confinement layer 132, p- (Al _0.5
Since it is the Ga _0.5 ) _0.5 In _0.5 P layer 135, the quality of the regrowth interface 135a deteriorates due to the influence of oxidation. As a result, there is a problem that current leakage occurs and the oscillation threshold value becomes high. Typically, it has a non-coated, resonator length of 400 μm, an oscillation threshold of 45 mA, and a kink level of 25 m.
About W.

In the semiconductor laser device shown in FIG. 12, the active layer 104 is bent at the end of the current confinement layer 102 to have a real refractive index guide structure. Loss is also reduced. For this reason, there is a problem that the kink level is rather lowered. Typically, it has a non-coating, resonator length of 400 μm, an oscillation threshold of 25 to 30 mA, and a kink level of about 20 mW.

It is an object of the present invention to provide a method for manufacturing a semiconductor light emitting device having a current confinement layer and capable of improving characteristics. The semiconductor light emitting device is a semiconductor laser device and a light emitting diode.

[0008]

According to a first aspect of the present invention, there is provided a method for manufacturing a semiconductor light emitting device, comprising the steps of:
Of a GaAs substrate having one of n-type or n-type conductivity
Providing a current confinement layer made of GaAs or AlGaAs having the other conductivity type of p-type or n-type on the (111) B plane or the off plane having the (111) B plane as a main surface; Forming a through-groove having a predetermined pattern from the surface of the current constriction layer to the substrate; and maintaining the substrate at a temperature in the range of 720 ° C. to 740 ° C., changing the one conductivity type to The third made of AlGaAs
The through-groove is embedded in the cladding layer, and the surface of the portion in which the through-groove is embedded is flush with the surface of the current confinement layer, and the portion in which the inside of the through-groove is embedded on the surface of the current confinement layer. And a step of growing a first clad layer, an active layer, and a second clad layer forming a double hetero structure on the entire surface of the substrate. I have.

According to a second aspect of the present invention, in the method of manufacturing a semiconductor light emitting device, the (111) B surface or the (111) B surface of the GaAs substrate having one of p-type and n-type conductivity is defined as the main surface. Providing a current confinement layer made of GaAs or AlGaAs having the other conductivity type of p-type or n-type on the off surface to be formed; and providing a predetermined confinement layer from the surface of the current confinement layer to the substrate on the current confinement layer. Forming a plurality of through-grooves in the pattern, and holding the substrate at a temperature of 720 ° C. or less, and forming an AlGa having one conductivity type in each of the through-grooves.
A third cladding layer made of As is grown so that each surface is flush with the surface of the current confinement layer,
The method is characterized by including a step of filling the through groove and a step of growing a first clad layer, an active layer, and a second clad layer having a double hetero structure on the entire surface of the substrate.

According to a third aspect of the present invention, there is provided a method for manufacturing a semiconductor light emitting device, wherein the (111) B surface or the (111) B surface of a GaAs substrate having one of p-type and n-type conductivity is defined as a main surface. Providing a current confinement layer made of GaAs or AlGaAs having the other conductivity type of p-type or n-type on the off surface to be formed; and forming a circular shape from the surface of the current confinement layer to the substrate on the current confinement layer. Forming a through-groove having the above-mentioned pattern, and holding the substrate at a temperature of 720 ° C. or lower, and forming the AlGaA having the one conductivity type in the through-groove.
growing a third cladding layer made of S.sub.s so that the surface is flush with the surface of the current confinement layer, and embedding the through-groove; and forming a first cladding layer having a double heterostructure on the substrate. The method is characterized by comprising a step of growing a layer, an active layer, and a second clad layer over the entire surface, and a step of processing the layer having the double hetero structure into a truncated cone.

[0011]

In the method of manufacturing a semiconductor light emitting device according to the first aspect, after forming a through groove in the current confinement layer, the substrate is heated to a temperature of 720.degree.
While maintaining the temperature within the range of 40 ° C., a third cladding layer made of AlGaAs having one conductivity type is buried in the through groove, and the surface of the portion in which the through groove is buried is the surface of the current confinement layer. And growing on the surface of the current constriction layer so as to have an extension portion thinner than a portion filling the through groove. Therefore, when a layer constituting a double hetero structure is formed thereon by, for example, MOCVD, the active layer is slightly bent at the edge of the through groove. As a result, the manufactured semiconductor light emitting device has a waveguide structure having the characteristics of the effective refractive index guide structure due to light absorption of the substrate (current constriction layer),
It has the characteristics of the actual refractive index guide structure due to the bending of the active layer, and has the advantages of the conventional example shown in FIGS. That is, the mode loss with respect to the basic mode and the effect of increasing the mode loss with respect to the higher-order mode occur, and the basic mode is further stabilized. Further, current leakage is reduced, and the oscillation threshold value is reduced.

According to a second aspect of the present invention, in the method for manufacturing a semiconductor light emitting device, a plurality of the through grooves are formed in the current confinement layer.
The third cladding layer is embedded in each of the through grooves. Therefore, during operation of the manufactured semiconductor light emitting device,
A plurality of oscillation regions are generated according to the current path formed by each through groove. That is, a semiconductor laser array is configured.

According to a third aspect of the present invention, in the method of manufacturing a semiconductor light emitting device, after forming a circular groove through the current confinement layer from the surface of the current confinement layer to the substrate, the temperature of the substrate is reduced. Is maintained at 720 ° C. or lower, a third cladding layer having the one conductivity type is placed in the through groove of the current confinement layer so that the surface is flush with the surface of the current confinement layer. The through-groove is buried by growing. A first cladding layer having a double hetero structure on the current confinement layer and the third cladding layer;
An active layer and a second cladding layer are formed. Thus, a surface-emitting type light emitting diode is formed. At this time, the layer forming the double hetero structure is formed by a known growth method, for example, MOC without an etching step.
Since it is formed flat with good controllability by the VD method, there is almost no variation in thickness. Therefore, the emission luminance-applied current characteristic of the manufactured light emitting diode is stabilized. Further, since the etching step is not interposed after the formation of the third cladding layer, the growth interface is not oxidized. Therefore, current leakage is reduced and light emission luminance is increased. Thus, the characteristics of the light emitting diode are improved. Further, since the layer forming the double hetero structure is processed into a truncated cone shape, the light extraction efficiency on the element surface increases.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments.

FIG. 1 shows a cross section of a semiconductor laser device on which the present invention is based. This semiconductor laser device
On the (111) B plane of the p-GaAs substrate 1, an n-GaAs current confinement layer (thickness 1 μm) 2 and p- (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P
A first cladding layer (0.2 μm thick) 3 and a non-doped Ga _0.5
In _0.5 P active layer (0.05 μm thick) 4 and n- (Al _0.5 Ga
_0.5 ) _0.5 In _0.5 P Second cladding layer (thickness: 1.5 μm) 5 and n
A -Ga _0.5 In _0.5 P contact layer (0.5 μm thickness) 6 is provided. Reference numeral 4a denotes an oscillation region (shown by oblique lines), and reference numerals 9 and 10 denote electrodes. In the center of the current confinement layer 2, a band-shaped through groove 2b extending in a direction perpendicular to the cross section is formed, and a p-Al _0.7 Ga _0.3 As third clad layer (having a thickness of 1.
3 μm) 8 is embedded. Surface 8a of cladding layer 8
And the surface 2a of the current confinement layer 2 are on the same plane.

Here, before explaining the manufacturing process of this element, the underlying phenomena will be described. The inventor of the present invention has proposed, by MOCVD, Ga having (111) B as a main surface.
Al _0.7 Ga _0.3 As on As substrate (conductivity type may be n or p)
Layer, Ga _0.5 an In _0.5 P layer was found to become as _{(Al 0.5 Ga 0.5) 0.5 In} 0.5 when the P layer is grown, the relationship between the growth rate and the substrate temperature of the respective layers in FIG. 4. Material during the growth of each layer, TMG (trimethyl gallium), TMA (trimethyl aluminum), TMI (trimethyl indium), and AsH ₃ (arsine), PH ₃ (phosphine).
In this experiment, during the growth of AlGaAs, the supply ratio of the group V element to the group III element (hereinafter referred to as “V / III ratio”) was set to 8.
0, Group III supply (sum of TMG and TMA supply) 1.6
× 10 ⁻⁵ mol / min, while GaInP and AlGaInP
When growing, the V / III ratio was set to 200 and the group III supply amount (TM
G × TMA + TMI) 2.0 × 10 ⁻⁵ mol
/ Min. Note that Al _x Ga _1-x As and (Al _x Ga _1-x ) _y In
_The same experiment was conducted for the Al composition ratio x changed with _1-y P (x = 0 to 1).
Approximately the same results as shown in FIG. 4 were obtained. As is apparent from FIG. 4, when the substrate temperature is 720 ° C. or lower, AlGaA
The s layer does not grow on the (111) B plane of the GaAs substrate at all.
On the other hand, the GaInP layer and the AlGaInP layer grow over a wide growth temperature range (650 to 750 ° C.), and the growth rate is substantially constant without depending on the substrate temperature. The above-described element manufacturing process utilizes this phenomenon.

The relationship between the growth rate of the GaAs substrate on the (111) B plane and the substrate temperature has been known for the growth of GaAs (Journal of Crystal Growth). ) Vo
l.94 (1989) pp 203-207 (hereinafter referred to as "Document 1")). FIG. 1 of Document 1 shows that the growth rate of GaAs is zero at a substrate temperature of 720 ° C. or lower, and is equal to or higher than the substrate temperature of 720 ° C., similarly to the growth rate of Al _x Ga _{1 -x} As shown in FIG. It is shown to stand up. However, what is described in Document 1 is only the characteristics relating to the growth of GaAs on the (111) B plane of the GaAs substrate.
It does not relate to the growth of lGaAs, GaInP or AlGaInP. On the other hand, as will be described later, the material of the third cladding layer 8 shown in FIG.
The effect of the present invention can be obtained only by adopting the above.
That is, the invention of the present application cannot be derived from the literature 1, and the invention of the present application was created only by discovering the phenomenon relating to the growth of AlGaAs, GaInP, and AlGaInP shown in FIG.

When actually manufacturing the above-mentioned semiconductor laser device, first, as shown in FIG.
11) On the surface B, an n-GaAs current confinement layer 2 is grown to 1 μm by a liquid phase growth method. Next, as shown in FIG.
Etching is performed to remove p− from the surface 2 a of the current confinement layer 2.
The through grooves 2b having a width of 4 μm and a depth of 1.3 μm reaching the GaAs substrate 1 are formed. In this example, the direction of the through groove 2b is

## EQU1 ## The direction was the [00] direction. Next, as shown in FIGS. 3 (c) and 3 (d), p-Al is formed on the substrate 1 by MOCVD.
_{A 0.7} Ga _0.3 As cladding layer 8 is grown. The growth conditions are
The substrate temperature was 700 ° C., and the V / III ratio was 80. As described with reference to FIG. 4, under this growth condition, the GaAs substrate 1
Since the growth rate on the (111) B plane is almost zero, AlGa
The As layer does not grow on the bottom of the through groove 2b and on the surface of the n-GaAs current confinement layer 2. Instead, the AlGaAs layer grows from the side wall of the through groove 2b toward the inside of the groove as shown in FIG. 4C, and the front of the layer grown from the periphery as shown in FIG. Then, the entire through groove 2b is filled. As a result, the surface 8a of each cladding layer 8 and the surface 2a of the current confinement layer 2 are on the same plane, and the surface side of the substrate 1 is flat. Subsequently, as shown in FIG. 4E, a p-AlGaInP cladding layer 3, a non-doped GaInP active layer 4, and an n-AlGaInP
A cladding layer 5 and an n-GaInP contact layer 6 are grown. The growth conditions were a substrate temperature of 700 ° C. and a V / III ratio of 200. At this time, the AlGaInP layer and the GaIn
Unlike the AlGaAs layer, the P layer also grows on the (111) B plane (according to the above growth conditions, the growth rate is 1.7).
μm / hour. ). Thereafter, electrodes 9 and 10 are formed on the back surface of the substrate 1 and the surface of the contact layer 6, respectively. Finally, the chip is divided into chips along the alternate long and short dash line in FIG.
The semiconductor laser device shown in FIG. 1 was obtained.

In this case, the p-AlGaInP cladding layer 3 is grown with good controllability by MOCVD.
Moreover, it is not etched. Therefore, the thickness d of the cladding layer 3 hardly varies. Therefore, the basic mode is stabilized. Further, since the etching step is not interposed, the growth interface is not oxidized. Therefore, current leakage is reduced and the oscillation threshold value is reduced. Further, since the thickness of the cladding layer 3 on the current confinement layer 2 is small, the loss of the higher-order mode does not decrease. Therefore, the kink level is improved. Actually, the manufactured semiconductor laser device oscillated without kink up to 50 mW at an oscillation threshold of 40 mA in a non-coated, resonator length of 400 μm. Oscillation wavelength is 679nm at 50mW output
Met. The conventional semiconductor laser device shown in FIG.
Non-coating, oscillation length of 45m with resonator length 400μm
A, The kink level was doubled compared to the case where the kink level was 25 mW.

For comparison, GaAs is used as the material of the third cladding layer, and has the same cross-sectional structure as the element shown in FIG. 1 by utilizing the phenomenon shown in FIG. An element was manufactured. However, this comparative device did not cause laser oscillation. This is because the gain required for laser oscillation could not be obtained because the third cladding layer was a GaAs layer. From this, it is understood that the material of the third cladding layer 8 must be AlGaAs as described above.

FIG. 2 shows a cross section of a modification of the semiconductor laser device of FIG. This semiconductor laser device has a p-G
aAs substrate 11

## EQU2 ## On the (111) B plane turned off by 2 ° in the [00] direction, an n-GaAs current confinement layer (1 μm thick) 12 and a p- (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P First cladding layer (0.2 μm thick)
m) 13, a non-doped (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P active layer (thickness 0.05 μm) 14, and n- (Al _0.7 Ga _0.3 ) _0.5
In _0.5 P second cladding layer (thickness: 1.5 μm) 15 and n-Ga
_0.5 In _0.5 P contact layer (0.5 μm thick) 16 and n-G
An aAs contact layer (thickness: 0.1 μm) 17 is provided. 1
4a is an oscillation area, 19 and 20 are electrodes. In the center of the current confinement layer 12, a band-shaped through groove 12b extending in a direction perpendicular to the cross section is formed.
An Al _0.7 Ga _0.3 As third cladding layer (thickness: 1.3 μm) 18 is embedded. The surface 18a of the cladding layer 18 and the surface 12a of the current confinement layer 2 are on the same plane.

This semiconductor laser device is different from that of FIG. 1 in that a p-GaAs substrate 11 is used.

## EQU3 ## The point that the layers 12, 13,... Are provided on the (111) B plane which is turned off by 2 ° in the [00] direction, and the n-GaAs contact layer 1 is further provided on the n-GaInP contact layer 16.
7 is provided. By providing this n-GaAs contact layer 17, an ohmic contact with the electrode can be easily made, and as a result, the element resistance can be reduced. Further, the structure of the double hetero structure is p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 13, non-doped (Al _0.1 Ga _0.9 ) _0.5 In _0.5 P active layer 14, n-
(Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 15. As a result, an oscillation wavelength of 650 nm is obtained.

In manufacturing this device, the substrate temperature is set to 700 ° C. and the layers from the cladding layer 18 to the contact layer 16 are formed as in the case of manufacturing the device shown in FIG. p
The surface 18a of the cladding layer 18 and the surface 12 of the current confinement layer 12 could be flush with each other despite being off by 2 ° from the (111) B plane of the -GaAs substrate 11. The contact layer 17 is heated on the surface of the contact layer 16 ((111) B of GaAs) while the substrate temperature is raised to 740 ° C. so that GaAs can grow on the (111) B surface.
Face).

In this semiconductor laser device, as in the case of FIG. 1, the fundamental mode is stabilized, the current leakage is reduced, the oscillation threshold value is reduced, and the kink level is improved. actually,
A chip cavity length 500μm by _{Al 2 O 3 λ / 2-} λ
In the state where the / 2 coating was performed, good characteristics such as an oscillation threshold value of 50 mA and a kink level of 45 mW were exhibited.

FIG. 3 shows a cross section of a semiconductor laser device manufactured by the manufacturing method according to the first embodiment of the present invention. This semiconductor laser device is formed on the p-GaAs substrate 31 (1).
11) An n-GaAs current confinement layer (1 μm thick) 32 on the B surface
And a third cladding layer of p-Al _0.7 Ga _0.3 As (thickness 0.02)
μm) 38 ′, p- (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P first cladding layer (0.2 μm thickness) 33 and non-doped Ga _0.38 In
_0.62 P layer (0.02 μm thickness) 34 and n- (Al _0.5 Ga _0.5 )
_0.5 In _0.5 P layer second cladding layer (thickness: 1.5 μm) 35 and n
A -Ga _0.5 In _0.5 P contact layer (0.5 μm in thickness) 36 is provided. 34a is an oscillation region, and 39 and 40 are electrodes. At the center of the current confinement layer 32, a band-like through groove 32b extending in a direction perpendicular to the cross section is formed.
2b, p-Al _0.7 Ga _0.3 As third cladding layer (thickness 1.
3 μm) 38 are embedded. The cladding layer 38 '
The extension portion is connected to the cladding layer 38 and covers the surface of the current confinement layer 32. Also, the cladding layer 38
And the surface 32a of the current confinement layer 32 are flush with each other.

This semiconductor laser device is different from that of FIG. 1 in that the active layer 4 has a strained structure with the composition of non-doped Ga _0.38 In _0.62 P, and that the substrate temperature during growth of the cladding layer 38 is 730 ° C. The difference is that the AlGaAs layer 38 'is slightly grown on the surface (the (111) B surface of GaAs) 32a of the current confinement layer 32 on both sides of the through groove 32b. As a result, as shown in the drawing, the active layer 34 is slightly bent on the edge of the through groove 32b. Thereby, the substrate (current constriction layer) is formed as a waveguide structure.
11 has both the characteristics of the effective refractive index guide structure due to the light absorption and the characteristics of the real refractive index guide structure due to the bending of the active layer, and has the advantages of the conventional example shown in FIGS. That is, this semiconductor laser device
The mode loss with respect to the basic mode and the effect of increasing the mode loss with respect to the higher-order mode occur, so that the basic mode can be further stabilized. Further, similarly to the first embodiment, the current leakage is reduced, the oscillation threshold value is reduced, and the kink level is improved.

In practice, the oscillation threshold value was 55 mA and the kink level was 220 mW (oscillation wavelength 690 nm) under the conditions that the resonator length was 600 μm, and the front and rear surface reflectivities were 8% and 70%, respectively. . This is because the kink level (1) of the conventional example shown in FIG.
(About 20 mW).

When this element is manufactured, a through-hole 32b is formed in the current confinement layer 32 in the same manner as in the case of manufacturing the element shown in FIG.
8 to the contact layer 36 are formed. By setting the substrate temperature to 730 ° C. in this way, the cladding layer 38 is grown in the through groove 32b so that the surface is flush with the surface of the current confinement layer 32, and the through groove 32b is buried. A through groove 32 is formed in the surface of the current confinement layer 32.
The extension portion 38 'having a thickness smaller than the thickness of the portion in which b is buried could be grown. Further, each of the layers 33,... Could be grown thereon at an appropriate growth rate, whereby the waveguide structure could be formed. In this case, the substrate temperature is preferably 720 to 740 ° C. If the temperature is lower than 720 ° C., the extension 38 ′ cannot be grown,
Is exceeded, the thickness of the extending portion 38 'becomes too thick.

FIG. 6 shows a cross section of another modification of the semiconductor laser device of FIG. This semiconductor laser device has p
On the (111) B face of the GaAs substrate 41, two layers 42 ', 4
A current confinement layer (1 μm thick) 42 made of 2 ″ and p- (Al
_0.5 Ga _0.5 ) _0.5 In _0.5 P First cladding layer (0.2 μm thick)
43 and a non-doped Ga _0.5 In _0.5 P active layer (with a thickness of 0.05
μm) 44, n- (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P layer second cladding layer (thickness 1.5 μm) 45 and n-Ga _0.5 In _0.5 P contact layer (0.5 μm thickness) 46 Have. 44a is an oscillation region, and 49 and 50 are electrodes. The current confinement layer 42
In the center of the band, a band-shaped through groove 4 extending in a direction perpendicular to this section is provided.
2b is formed, and p-Al _0.7 Ga is formed in the through groove 42b.
_{A 0.3} As third cladding layer (thickness: 1.3 μm) 48 is embedded. The surface 48a of the cladding layer 48 and the current confinement layer 42
Is flush with the surface 42a.

This semiconductor laser device is different from that of FIG. 1 in that the current confinement layer 42 is formed of n-Al _0.1 Ga _0.9 As (thickness 0.9).
.mu.m) 42 'and n-GaAs (0.1 .mu.m thick) 42 ".
The difference is in the layer configuration. When manufacturing this semiconductor laser device, n-Al _0.1 Ga _0.9 As (thickness _0.9 μm)
m) 42 'and n-GaAs (0.1 .mu.m thick) 42 "are formed, and a through groove 42b is formed at the center of the element from the surface of the layer 42" to the substrate 41. Next, on the substrate 41, the MOCV
An AlGaAs layer is grown by the D method. Current confinement layer 42
Of the n-Al _0.1 Ga _0.9 As layer 4
Even when 2 'is exposed, as in the first embodiment, at a substrate temperature of 720.degree. C. or lower, selective growth occurred to fill only the inside of the through groove 42b. In addition, such selective growth is performed by Al
The Al composition ratio of the GaAs current confinement layer is from zero to at least 0.5.
It was realized until 3. Then, by MOCVD method,
By growing the respective layers 43,...
2 and the effective refractive index guide structure by light absorption of the substrate 1 can be formed with good controllability.

As a result, this semiconductor laser device is also shown in FIG.
As in the first embodiment, the fundamental mode was stabilized, the current leakage was reduced, the oscillation threshold was lowered, and the kink level was improved.

FIG. 7 shows a cross section of still another modification of the semiconductor laser device of FIG. This semiconductor laser device is formed on an (111) B surface of a p-GaAs substrate 51 by n-GaAs.
The current confinement layers (thickness 1 μm) 52 and 52 ′ and p- (Al _0.5 Ga
_0.5 ) _0.5 In _0.5 P First cladding layer (0.2 μm thickness) 53
And a non-doped Ga _0.5 In _0.5 P active layer (0.05 μm thick)
54, an n- (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P layer, a second cladding layer (thickness 1.5 μm) 55, and an n-Ga _0.5 In _0.5 P contact layer (thickness 0.5 μm) 56. I have. 54a is an oscillation region, and 59 and 60 are electrodes. In the center of the current confinement layer 52, a band-shaped through groove 52b extending in a direction perpendicular to the cross section is provided.
Are formed. N is provided on the inner peripheral portion of the through groove 52b.
The GaAs current confinement layer extension 52 'is embedded, and p-Al _0.7 Ga _0.3 As third
A cladding layer (thickness: 1.3 μm) 58 is embedded. The surface 58a of the cladding layer 58 and the current confinement layers 52, 52 '
Are coplanar with the surfaces 52a and 52a '.

In manufacturing this semiconductor laser device, after forming a through groove (width 4 .mu.m) 52b, the n-GaAs current confinement layer extension 52 'is first formed by MOCVD so that the remaining width of the through groove becomes 2.5 .mu.m. The GaAs buried layer 58 is grown laterally until the buried layer 58 is grown. After this, M
Each layer 53,... Is grown by the OCVD method in the same manner as in the case of manufacturing the structure shown in FIG.

In this semiconductor laser device, an effective refractive index guide structure can be formed with good controllability, as in FIG. 1, the fundamental mode is stabilized, the current leakage is reduced, the oscillation threshold is reduced, and the kink level is reduced. Is improved. Moreover, the through groove 5
Since the current injection width is reduced by forming the current confinement layer extension 52 'in 2b, the oscillation threshold value is further reduced and the astigmatic difference is further reduced than in FIG. Actually, while the semiconductor laser device of FIG. 1 had an oscillation threshold of 40 mA and an astigmatic difference of 5 μm (at 3 mW) at an uncoated, resonator length of 400 μm, the semiconductor laser device had the same conditions. Indicate an oscillation threshold of 30 mA and an astigmatic difference of 0 μm (at 3 mW).

FIG. 8 shows a cross section of a semiconductor laser device manufactured by the manufacturing method according to the second embodiment of the present invention. This semiconductor laser device is formed on the p-GaAs substrate 61 (1).
11) On the surface B, an n-GaAs current confinement layer (thickness: 1 μm) 62
, P- (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P first cladding layer (thickness 0.2 μm) 63 and a non-doped Ga _0.5 In _0.5 P active layer
(Thickness 0.05 μm) 64 and n− (Al _0.5 Ga _0.5 ) _0.5 In _0.5
P-layer second cladding layer (thickness: 1.5 μm) 65, n-Ga _0.5
An In _0.5 P contact layer (thickness: 0.5 μm) 66 is provided. 64a is an oscillation region, and 69 and 70 are electrodes. Three band-shaped through-grooves 62b, 62 extending in the direction perpendicular to the cross-section are provided at the center and both sides of the current confinement layer 62, respectively.
b, 62b (groove width 3.5 μm, groove pitch 5.5 μm) are formed, and a p-Al _0.7 Ga _0.3 As third cladding layer (thickness 1.3 μm) 68 is embedded in each through groove 62b. I have. Surface 68a of cladding layer 68 and surface 62a of current confinement layer 62
And are in the same plane.

This semiconductor laser device has exactly the same layer configuration as that of FIG. 1, but has a plurality of through grooves 62b serving as current paths in the current confinement layer 62, and accordingly a plurality of oscillation regions 64a. Having a semiconductor laser array. In this semiconductor laser device, oscillation in a 180 ° phase mode was observed up to a high optical output of 350 mW.

In manufacturing this semiconductor laser device, after a current confinement layer 62 is provided on a substrate 61, the plurality of through-grooves 62b are formed in the current confinement layer 62 at the same time.
After that, the third cladding layer 68 is buried in each of the through grooves 62b,..., And layers 63,.

FIG. 9 shows a cross section of still another modification of the semiconductor laser device of FIG. This semiconductor laser device is provided on an (111) B surface of a p-GaAs substrate 71 by n-GaAs.
The current confinement layer (thickness: 1 μm) 72 and p- (Al _0.5 Ga _0.5 ) _0.5
An In _0.5 P first cladding layer (0.2 μm in thickness) 73, a non-doped Ga _0.5 In _0.5 P active layer (0.05 μm in thickness) 74,
-(Al _0.5 Ga _0.5 ) _0.5 In _0.5 P layer A second clad layer (thickness: 1.5 μm) 75 and an n-Ga _0.5 In _0.5 P contact layer (thickness: 0.5 μm) 76 are provided. 74a is an oscillation region, 7
9, 80 are electrodes. In the center of the current confinement layer 72, a band-shaped through groove (current path) 72b extending in a direction perpendicular to the cross section is formed. A p-Al _0.7 Ga _0.3 As third cladding layer (thickness: 1.3 μm) is provided in the through groove 72b.
78 is embedded. On both sides of the current confinement layer 72, a band-shaped non-penetrating groove 72 extending in a direction perpendicular to the cross section is provided.
b 'are formed at a predetermined pitch, and each non-penetrating groove 72b'
P-Al _0.7 Ga _0.3 As fourth cladding layer 78 'is embedded within. The surface 78a of each cladding layer 78, 78 ',
78a 'and the surface 72a of the current confinement layer 72 are on the same plane.

In manufacturing this semiconductor laser device, after a current confinement layer 72 is provided on a substrate 71, the current confinement layer 72 is formed.
The non-through groove 72 that stays in the current constriction layer 72
b ', ... are formed. Next, a through groove 72b extending from the surface of the current confinement layer 72 to the substrate 71 is formed in the current confinement layer 72. Thereafter, the substrate 1 is kept at a temperature of 700 ° C. as in the case of manufacturing the device shown in FIG. In this state, the cladding layers 78, 78 ',... Are formed in the through-grooves 72b and the non-through-grooves 72b', respectively.
Are grown at the same time so as to be flush with the surface of the trench, and the through groove 72b and the non-through groove 72b 'are buried. After this,
1, a clad layer 73, an active layer 74, and a clad layer 75 are grown on the entire surface of a substrate 71.

This semiconductor laser device has exactly the same layer structure as that of FIG. 1, except that a plurality of through grooves 72b and a plurality of non-through grooves 72b 'are provided in the current confinement layer 72. The central through-groove 72 b reaches the substrate 71 from the surface of the current confinement layer 72, while the non-perforated grooves 72 b ′ on both sides remain in the current confinement layer 72. There is only one through groove 72b for forming the oscillation region, and the other non-through groove 7b
2b ',... Are for eliminating distortion due to the layer structure. That is, in the semiconductor laser device of FIG. 1, all the strain is applied to the portion of the active layer 4 on the edge of the through groove 2b (boundary of the oscillation region 4a). Since there are a plurality of through grooves 72b ', (and AlGaAs layers embedded in each groove),
The strain applied to the active layer 74 is dispersed on each of the grooves 72b ',. Therefore, the strain applied to the oscillation region 74a is reduced, and as a result, the long-term reliability of the device is improved.

FIG. 10 shows a surface-emitting type light emitting diode manufactured by the manufacturing method according to the third embodiment of the present invention (FIG. 10A is a cross section, and FIG. ) Is seen from above.) This light emitting diode is formed on the (111) B surface of the p-GaAs substrate 81 by n-GaAs.
The current confinement layer 82 and p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P first
Cladding layer 83 and non-doped (Al _0.45 Ga _0.55 ) _0.5
In _0.5 P active layer 84 and n- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P
A second cladding layer 85 and an n-Ga _0.5 In _0.5 P contact layer 86 are provided. 89 and 90 are electrodes. In the center of the current confinement layer 82, a circular pattern through groove 82b is formed.
Is formed, and p-Al _0.7 Ga _0.3 is formed in the through groove 82b.
An As third cladding layer 88 is embedded. The surface 88a of the cladding layer 88 and the surface 82a of the current confinement layer 82 are flush with each other. The central portion of the cladding layer 85 is processed into a truncated cone by an ion milling method.

The current constriction layer 82, the through groove 82b, and the cladding layer 88 are formed in exactly the same steps as in the semiconductor laser device of FIG. Therefore, the clad layer 83, the active layer 84, and the clad layer 85 having the double hetero structure can be formed with good controllability, and as a result, the emission luminance-applied current characteristics are stabilized. Further, since the etching step is not interposed after the formation of the cladding layer 88, the growth interface is not oxidized. Therefore, current leakage is reduced and light emission luminance is increased. Thus, the characteristics of the light emitting diode can be improved. Further, the contact layer 86 and the upper electrode 90 have a small area circular pattern provided in the truncated cone portion of the cladding layer 85. Thereby, the light extraction efficiency from the element surface can be increased.

Actually, when this light emitting diode was molded into a 5 mmφ package and energized at 20 mA, a luminous intensity of 4 candela (wavelength: about 0.3 candela) was obtained at a wavelength of 555 nm.

In each of the above examples, the GaAs substrate is of p-type, but it is needless to say that the present invention is not limited to this. Ga
The conductivity type of the As substrate may be either p-type or n-type, and the conductivity type of each growth layer may be determined according to the conductivity type of the GaAs substrate. The laser oscillation wavelength can be selected from a red to orange wavelength band by appropriately selecting the composition of the AlGaInP active layer. The active layer does not necessarily need to be non-doped, and may be p-type or n-type. The structure of the double hetero layer may be a SCH (separate confinement hetero structure) structure in which a guide layer is inserted as necessary, or a multi-quantum well structure or a multi-quantum barrier structure may be employed. . GaInP or G
A contact layer of aAs can also be provided as needed. In addition, the GaAs substrate does not need to be in the just direction as long as (111) B is the main surface,

(Equation 4) May be turned off several times. Further, Al is contained in the current confinement layer.
The layer growth after embedding the GaAs layer is preferably performed by the MOCVD method. Other vapor phase growth methods may be used.

[0045]

As is apparent from the above description, in the method for manufacturing a semiconductor light emitting device according to the first aspect, after forming a through groove in the current confinement layer, the substrate is kept at a temperature within the range of 720 ° C. to 740 ° C. In this state, a third cladding layer made of AlGaAs having one conductivity type is buried in the through-groove, and the surface of the portion in which the through-groove is buried is flush with the surface of the current confinement layer. On the surface of the constriction layer, the growth is made so as to have an extension portion thinner than the portion filling the through groove.
When a layer constituting the double hetero structure is formed by the method, the active layer is slightly bent at the edge of the through groove. As a result, the manufactured semiconductor light emitting device has both the characteristics of the effective refractive index guide structure due to light absorption of the substrate (current constriction layer) and the characteristics of the real refractive index guide structure due to bending of the active layer as a waveguide structure. Therefore, the basic mode can be further stabilized by the reduction of the mode loss for the basic mode and the effect of increasing the mode loss for the higher-order mode. In addition, current leakage can be reduced, and the oscillation threshold can be lowered.

According to a second aspect of the present invention, in the method of manufacturing a semiconductor light emitting device, a plurality of the through grooves are formed in the current confinement layer.
Since the third cladding layer is embedded in each of the through-grooves, a plurality of oscillation regions can be generated according to the current path formed by each of the through-grooves during operation of the manufactured semiconductor light emitting device. That is, a semiconductor laser array can be configured.

According to a third aspect of the present invention, in the method for manufacturing a semiconductor light emitting device, a circular groove extending from the surface of the current confinement layer to the substrate is formed in the current confinement layer. Is maintained at 720 ° C. or lower, a third cladding layer having the one conductivity type is placed in the through groove of the current confinement layer so that the surface is flush with the surface of the current confinement layer. The first cladding layer, the active layer, and the second cladding layer having a double hetero structure are formed on the current confinement layer and the third cladding layer by growing the semiconductor layer. Thus, a surface-emitting type light emitting diode can be configured. At this time, the layer having the double hetero structure is formed by a known growth method, for example, MOCV without interposing an etching step.
Since it is formed flat with good controllability by the method D, there is almost no variation in thickness. Therefore, the light emission luminance-applied current characteristic of the manufactured light emitting diode can be stabilized. Further, since the etching step is not interposed after the formation of the third cladding layer, the growth interface is not oxidized. Therefore, the light emission luminance can be increased by reducing the current leakage, and the characteristics of the light emitting diode can be improved. Further, since the layer forming the double hetero structure is processed into a truncated cone shape, the light extraction efficiency on the element surface can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section of a semiconductor laser device on which the present invention is based.

FIG. 2 is a view showing a cross section of a modification of the semiconductor laser device of FIG. 1;

FIG. 3 is a diagram showing a cross section of a semiconductor laser device manufactured by the manufacturing method according to the first embodiment of the present invention;

FIG. 4 shows Al on a (111) B surface of a GaAs substrate.
FIG. 4 is a diagram showing the relationship between the growth rate of each layer of GaAs, GaInP, and AlGaInP and the substrate temperature.

FIG. 5 is a diagram illustrating a manufacturing process of the semiconductor laser device of FIG. 1;

FIG. 6 is a diagram showing a cross section of another modification of the semiconductor laser device of FIG. 1;

FIG. 7 is a diagram showing a cross section of still another modification of the semiconductor laser device of FIG. 1;

FIG. 8 is a diagram showing a cross section of a semiconductor laser device manufactured by a manufacturing method according to a second embodiment of the present invention.

FIG. 9 is a diagram showing a cross section of still another modification of the semiconductor laser device of FIG. 1;

FIG. 10 is a diagram showing a cross section and a surface of a light emitting diode manufactured by a manufacturing method according to a third embodiment of the present invention.

FIG. 11 is a diagram showing a cross section of a conventional effective refractive index guide type semiconductor laser device.

FIG. 12 is a diagram showing a cross section of a conventional real refractive index guide type semiconductor laser.

[Explanation of symbols]

1,11,21,31,41,51,61,71,81 p-Ga
As substrate 2,12,22,32,42 ", 52,62,72,82 n-
GaAs current confinement layer 2b, 12b, 22b, 32b, 42b, 52b, 62b, 72b, 82
b Through-groove 3,13,23,33,43,53,63,73,83 First cladding layer 4,14,24,34,44,54,64,74,84 Active layer 5,15,25,35 , 45, 55, 65, 75, 85 Second cladding layer 8, 18, 28, 38, 48, 58, 68, 78, 88 p-AlGaAs third cladding layer 38 'p-AlGaAs Third cladding layer extension Part 42 'n-AlGaAs current confinement layer 52' n-GaAs current confinement layer extension 72b 'non-through groove 78' p-AlGaAs fourth cladding layer

Continuation of front page (56) References JP-A-6-350195 (JP, A) JP-A-57-24591 (JP, A) JP-A-4-74488 (JP, A) JP-A-4-100290 (JP) JP-A-5-343794 (JP, A) JP-A-64-30286 (JP, A) JP-A-3-133190 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) H01S 5/00-5/50 H01L 33/00 JICST file (JOIS)

Claims (3)

(57) [Claims] 1. A p-type or n-type GaAs substrate having a (111) B surface or an off-surface having a (111) B surface as a main surface, the other surface of which is p-type or n-type. Providing a current confinement layer made of GaAs or AlGaAs having a conductivity type; forming a through groove of a predetermined pattern from the surface of the current confinement layer to the substrate in the current confinement layer; The third cladding layer made of AlGaAs having the one conductivity type is buried in the through-groove while the temperature is kept in the range of ℃ to 740 ° C., and the surface of the portion where the through-groove is buried has the current constriction. Growing on the surface of the current constriction layer so as to have an extending portion thinner than a portion filling the through groove on the surface of the current confinement layer; and forming a double hetero structure on the substrate. Eggplant first crack A method for manufacturing a semiconductor light emitting device, comprising a step of growing a first layer, an active layer, and a second clad layer over the entire surface. 2. A p-type or n-type GaAs substrate having a (111) B surface or an off-surface having a (111) B surface as a main surface, the other surface of which is p-type or n-type. Providing a current blocking layer made of GaAs or AlGaAs having a conductivity type; forming a plurality of through-grooves of a predetermined pattern from the surface of the current blocking layer to the substrate in the current blocking layer; In a state where the temperature is maintained at 720 ° C. or lower, a third cladding layer made of AlGaAs having one of the above-mentioned conductivity types is placed in each of the through-grooves so that their surfaces are flush with the surface of the current confinement layer. And burying the through-grooves, and growing a first clad layer, an active layer and a second clad layer having a double heterostructure on the entire surface of the substrate. Light emitting element Production method. 3. A p-type or n-type GaAs substrate having a (111) B surface or an off-surface having a (111) B surface as a main surface, the other surface of which is p-type or n-type. Providing a current confinement layer made of GaAs or AlGaAs having a conductivity type; forming a through-groove in a circular pattern from the surface of the current confinement layer to the substrate in the current confinement layer; While maintaining the temperature at 720 ° C. or lower, a third cladding layer made of AlGaAs having one conductivity type is grown in the through groove so that the surface is flush with the surface of the current confinement layer. Burying the through-groove; growing a first clad layer, an active layer and a second clad layer forming a double hetero structure on the entire surface of the substrate; and forming the double hetero structure layer on the substrate. Process into a truncated cone The method of manufacturing a semiconductor light emitting device characterized by having a step.