JP2975745B2 - Surface emitting semiconductor laser device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-emitting type semiconductor laser device for taking out light output in a direction perpendicular to a substrate as a cavity direction and a method of manufacturing the same.

[0002]

2. Description of the Related Art Along with a demand for higher integration of electronic devices, a resonator is formed by an epitaxial surface epitaxially grown on a substrate and a substrate surface, and laser light is emitted in a direction perpendicular to the substrate surface (epitaxial growth direction). Surface emitting semiconductor laser devices that emit light have been developed. Such a surface emitting semiconductor laser device is disclosed in, for example, JJ Appl. Phys. Lett., Vo.
l.28, No.4, (1989), pp.L667-L668 and in the 1990 Spring Conference of the Japan Society of Applied Physics 29a-SA-11.

FIG. 4 is a sectional view showing an example of a conventional surface-emitting type semiconductor laser device.

In FIG. 1, reference numeral 1 denotes an n-type GaAs substrate. On this substrate 1, a reflecting mirror layer (n-type GaAlAs layer / AlA
a plurality of pairs of s layers) 2, an n-type cladding layer (n-type GaAlA)
s) 3 is formed in this order. On the n-type cladding layer 3, an active layer (p-type GaAs) 4, a p-type cladding layer (p-type GaAlAs) 5, and a cap layer (p-type GaAs)
1As) 6 is formed, and a first current block layer (p-type G layer) is formed on the n-type cladding layer 3 in such a manner that the mesa-shaped buried portion 7 is buried.
aAlAs) 109 and a second current blocking layer (n-type Ga
A buried portion 11 made of (AlAs) 110 is formed. A planarization layer (p-type GaAlAs) 12 is formed on the cap layer 6 and the second current block layer 110. A contact layer (p-type GaAs) is formed on the planarizing layer 12.
lAs ) 13 and Si surrounding the contact layer 13
An insulating layer 14 formed by laminating a plurality of O ₂ films / TiO ₂ films is formed. On this contact layer 13, a dielectric multilayer reflector layer 15 composed of a plurality of pairs of SiO ₂ film / TiO ₂ film is formed.

A p-type electrode 16 made of Au / Cr is formed from the contact layer 13 to the insulating layer 14 so as to surround the reflecting mirror layer 15, and an n-type electrode 17 made of Au / Sn is formed on the substrate 1. Is formed on the lower surface.

In such a surface emitting laser device, the p-type current in the first current blocking layer 109 and the second current blocking layer 110 is controlled so that the current is concentrated in the mesa-shaped buried portion 7 having the active layer.
Current blocking is performed by the n reverse bias characteristic.

[0007]

However, in the above-described surface-emitting type semiconductor laser device, when the first current blocking layer 109 is formed, as shown in FIG. Parts or pits may occur.
In this case, the current blocking in these thin portions and the pits is remarkably reduced, and an invalid current that does not pass through the mesa-shaped buried portion 7 is increased. Therefore, there is a problem that the light output efficiency is poor.

[0008]

A surface-emitting type semiconductor laser device according to the present invention includes a buried portion including an active layer and a first current block formed around the buried portion and having the same conductivity type as the active layer. A surface-emitting type semiconductor laser device having a buried portion formed by laminating a second current blocking layer having a conductivity type opposite to that of an active layer, wherein the buried portion is separated from the buried portion and below the first current blocking layer. And an auxiliary current blocking layer made of the same material as the active layer.

A method for manufacturing a surface emitting semiconductor laser device according to the present invention comprises the steps of: forming a growth layer including an active layer in a mesa shape; and melt-backing the exposed active layer. In the manufacturing method, after forming a groove around a mesa-shaped portion of the active layer, the active layer is melted back.

[0010]

As described above, when the auxiliary current block layer of the same conductivity type as the first current block layer is formed under the first current block layer, separated from the buried portion including the active layer, the first current block layer The unevenness of the thickness of the auxiliary current block layer and the pits are compensated for each other, so that the unevenness of the current block layer can be reduced.

Further, as described above, if a groove is formed around a mesa-shaped portion of the active layer and the active layer is melted back, an auxiliary current blocking layer can be easily formed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a surface-emitting type semiconductor laser device of the present embodiment.

In FIG. 1, reference numeral 1 denotes an n-type GaAs substrate having a length of about 300 to 600 μm. On this substrate 1, n-type Ga
_A reflector layer 2 composed of a plurality of laminated layers of _0.9 Al _0.1 As layer / AlAs layer, a layer thickness 0.5 composed of n-type Ga _0.6 Al _0.4 As
A μm n-type cladding layer 3 is formed in this order.

On the n-type cladding layer 3, p-type GaAs
active layer 4 of 2 μm thick and p-type Ga_0.6Al_0.4
0.5 μm thick p-type cladding layer 5 made of As and p-type
Ga _0.94Al_0.060.5 μm thick cap made of As
Embedded in a mesa shape having a width W of about 10 μm,
An embedded portion 7 is formed, and the embedded portion 7 has a width D.
Desirably, it is about 10 μm, for example, 20 μm apart.
Is smaller than the active layer, for example, an active layer 4 having a thickness of 0.5 μm.
Auxiliary current blocking layer made of p-type GaAs of the same material
(P carrier concentration: 7 × 10¹⁷~ 1 × 10¹⁸cm^-3) 8
Are formed. The n-type cladding layer 3 and the auxiliary
On the current block layer 8, the mesa-shaped buried portion 7 is formed.
Embedded in the p-type Ga_0.55Al_0.45From As
One current block layer (p carrier concentration: 5 × 10¹⁷~ 7 ×
10¹⁷cm^-39) and n-type Ga_0.45Al_0.55As (n key
Carrier concentration: 5 × 10¹⁷~ 7 × 10¹⁷cm^-3Consisting of
The second current blocking layer 10 is formed in this order, and
Flow block layer 8, and first and second current block layers 9, 1
Embedded portions 11 made of 0 are formed in this order.
Here, the first current block layer on the auxiliary current block layer 8
The layer thickness of the auxiliary block layer 8 and the first current block layer 9
Is set so that the total thickness of the layers is less than or equal to the active layer 4.
For example, it is about 0.5 μm.
The layer thickness of the second current blocking layer 10 on the blocking layer 8 is 2 μm.
You. Therefore, the auxiliary current blocking layer 8 having the same conductivity type
And the first current blocking layer 9, and the second
Current blocking due to reverse bias characteristics in current blocking layer 10
Is performed.

On the cap layer 6 and the second current blocking layer 10, a planarizing layer 1 made of p-type Ga _0.6 Al _0.4 As
2 is formed, and p-type Ga _0.94 Al is formed on the planarizing layer 12.
_A contact layer 13 made of _0.06 As and an insulating layer 14 formed of a plurality of pairs of a SiO ₂ layer / TiO ₂ layer surrounding the contact layer 13 are formed. This contact layer 1
A dielectric multilayer reflector layer 15 composed of a plurality of pairs of SiO ₂ layers / TiO ₂ layers is formed on 3.

A p-type electrode 16 made of Au / Cr is formed from the contact layer 13 to the insulating layer 14 so as to surround the reflecting mirror layer 15, and an n-type electrode 17 made of Au / Sn is formed on the substrate 1. Is formed on the lower surface.

Next, a method for manufacturing such a semiconductor laser device will be described.

First, as shown in FIG.
Metal organic chemical vapor deposition (MOCVD) on As substrate 1
Alternatively, a growth layer is formed by using a molecular beam epitaxy method (MBE method) or the like. That is, the n-type Ga _0.9 Al _0.1 As layer and A
Reflector mirror layer 2 composed of a plurality of pairs of lAs layers, n-type Ga _0.6
0.5 μm-thick n-type cladding layer 3 made of Al _0.4 As, layer thickness K made of p-type GaAs, for example, active layer 4 having a thickness of 2 μm, layer thickness 0.5 μm made of p-type Ga _0.6 Al _0.4 As
m-type p-type cladding layer 5, a 0.5-μm-thick cap layer 6 made of p-type Ga _0.94 Al _0.06 As, and p-type Ga _0.55
A mask layer 18 made of Al _0.45 As and having a layer thickness of 0.2 μm is continuously grown in this order.

Subsequently, as shown in FIG. 2B, after a first resist layer 19 corresponding to the mesa-shaped buried portion 7 is formed on the mask layer 18 by patterning, the first resist layer 19 is masked. The first resist layer 19 is formed by etching such as ion beam etching, reactive ion etching, or reactive ion beam etching.
The mask layer 18, the cap layer 6, and the p-type cladding layer 5 below the portion where no is formed are completely removed, and the active layer 4 has a depth smaller than the layer thickness, for example, an inner diameter of 10 μm.
A groove 20 having an outer diameter of 50 μm is formed. After that, the first resist layer 19 is removed. Here, the layer thickness of the active layer 4 under the groove 20 is M.

Thereafter, as shown in FIG. 2C, a second resist layer 21 is formed on the mask layer 6 inside the groove 20 and in the groove 20.

Next, as shown in FIG.
Using the resist layer 21 as a mask, the second resist layer 2
The mask layer 18, the cap layer 6, and the p-type cladding layer 5 in the portion where 1 is not formed are completely removed. here,
A part of the surface of the active layer 4 may be removed by this chemical etching, and the layer thickness is set to L. Here, the layer thicknesses K, L, and M are set so as to satisfy the relationship of M + 0.5 μm ≦ L ≦ K. Thereafter, selection L using an unsaturated two-element mixed melt composed of Ga and As (hereinafter referred to as GaAs melt)
The hatched portion 41 of the active layer 4 is removed by the PE method (melt back) to remove the groove 20 of the n-cladding layer 3.
A mesa-shaped buried portion 7 composed of the active layer 4, the p-type cladding layer 5, and the cap layer 6 is formed while exposing a lower portion and leaving the mask layer 18, and a portion around the buried portion 7 is formed. An auxiliary current blocking layer 8 having a thickness of, for example, 0.5 μm is formed leaving a part of the active layer 4 apart by 20 μm.

Subsequently, as shown in FIG. 3B, the exposed n is selected by the selective LPE method using the mask layer 18 as a mask.
P-type Ga on the p-type cladding layer 3 and the auxiliary current blocking layer 8
The first current blocking layer 9 and n-type Ga are formed from _0.55 Al _0.45 As.
_A second current blocking layer 10 made of _0.45 Al _0.55 As is formed in this order, and the auxiliary auxiliary current blocking layer 8 and the first,
After forming the buried portion 11 including the second current blocking layers 9 and 10, the mask layer 18 is removed by a chemical etching method using a sulfuric acid etching solution or the like. Here, the first and second current blocking layers 9 and 1 on the auxiliary current blocking layer 8
The layer thicknesses of 0 are, for example, 0.5 μm and 2 μm, respectively.

Next, as shown in FIG. 1, p-type Ga _0.6 A
planarization layer 12 of l _0.4 As and p-type Ga _0.94 Al
_{After the} contact layer 13 made of _0.06 As is formed by the LPE method, the periphery of the contact layer 13 is removed, and the flattening layer 12 is exposed at the removed portion. Thereafter, a SiO ₂ film serving as a reflective layer and an insulating layer is formed on the planarizing layer 12 and the contact layer 13 by vapor deposition, sputtering, or the like.
A plurality of pairs of iO ₂ films are formed. Then, the SiO ₂ film formed in the peripheral portion on the contact layer 13 and the Ti
After removing the O ₂ film to form the insulating layer 14 and the reflective layer 15, a Cr film and an Au film are formed in this order to form the p-type electrode 16. Further, an Sn film and an Au film are formed in this order on the lower surface of the substrate 1 to form the n-type electrode 17, thereby completing the semiconductor laser device.

In such a surface-emitting type semiconductor laser device, an auxiliary current block layer of the same conductivity type as the first current block layer and made of the same material as the active layer is separated from the buried portion including the active layer. Since the first current block layer and the auxiliary current block layer are formed below the first current block layer, the thickness of the first current block layer and the auxiliary current block layer can be compensated for, and the unevenness of the pits can be reduced.

Here, since the auxiliary current blocking layer made of the same material as the active layer is separated from the buried portion including the active layer, there is no fear that a current flows from the buried portion to the auxiliary current blocking layer.

In the method of manufacturing a surface emitting semiconductor laser device, a groove is formed around a mesa-shaped portion of the active layer, and the active layer is melted back to form an auxiliary current blocking layer. Therefore, there is an effect that the manufacturing process is easy, and even if there are pits or the like in the auxiliary current block layer, the auxiliary current block layer is repaired by the regrown first current block layer. Further, since the first current blocking layer is formed between the buried portion and the auxiliary current blocking layer in the vicinity of the buried portion, the first current blocking layer is formed as compared with the case where the auxiliary block layer contacts the buried portion. Can be prevented from contacting the p-cladding layer.

Although the active layer is of the p-type in the above embodiment, it may be of the n-type. However, in this case, the first and second current block layers, the auxiliary block layers, and the like also need to have the opposite conductivity types. Further, the present invention can be applied to a surface emitting semiconductor laser device using a material other than GaAlAs, and furthermore, a buried type surface emitting semiconductor such as JJAppl.Phys.Lett., Vol. 28, No. 4, (1989). It can be appropriately used for various surface emitting semiconductor laser devices such as a laser device.

[0028]

According to the surface emitting semiconductor laser device of the present invention, an auxiliary current blocking layer of the same conductivity type as the first current blocking layer is separated from the embedded portion including the active layer, and is formed below the first current blocking layer. Therefore, the first current blocking layer and the auxiliary current blocking layer compensate for the unevenness of the film thickness and the pits, so that the unevenness of the current blocking layer can be reduced.

Further, in the surface emitting semiconductor laser device according to the present invention, the auxiliary current blocking layer is easily formed by forming a groove around a mesa-shaped portion of the active layer and then melt-backing the active layer. it can.

[Brief description of the drawings]

FIG. 1 is a sectional view of a surface-emitting type semiconductor laser device according to an embodiment of the present invention.

FIG. 2 is a process diagram showing a manufacturing process of the surface-emitting type semiconductor laser device.

FIG. 3 is a process diagram showing a manufacturing process of the surface-emitting type semiconductor laser device.

FIG. 4 is a sectional view of a conventional surface emitting semiconductor laser device.

FIG. 5 is a sectional view of a conventional surface emitting semiconductor laser device.

[Explanation of symbols]

 Reference Signs List 3 clad layer 4 active layer 7 buried portion 8 auxiliary block layer 9 first block layer 10 second block layer 11 buried portion

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Teruaki Miyake 2-18-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-2-177489 (JP, A) JP-A Heihei 2-66986 (JP, A) JP-A-3-105991 (JP, A) JP-A-61-40077 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01S 3/18 JICST file (JOIS)

Claims (2)

(57) [Claims] An embedded portion including an active layer, a first current blocking layer formed around the embedded portion and having the same conductivity type as the active layer, and a second current blocking layer having a conductivity type opposite to the active layer. In the surface-emitting type semiconductor laser device having a buried portion formed by laminating, an auxiliary current block layer made of the same material as the active layer is provided under the first current block layer and separated from the buried portion. A surface-emitting type semiconductor laser device characterized in that: 2. A method for manufacturing a surface-emitting type surface emitting semiconductor laser device, comprising the steps of: forming a growth layer including an active layer in a mesa shape; and melt-backing the exposed active layer. A method for manufacturing a surface-emitting semiconductor laser device, comprising: forming a groove in the periphery of a shape-like portion; and melt-backing the active layer.