JP2937060B2 - Algainp based light emission 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 semiconductor light emitting device using a compound semiconductor, and more particularly to a semiconductor light emitting device using AlGaInP as an active layer.

[0002]

2. Description of the Related Art An AlGaInP-based material has the largest direct transition band gap in a mixed crystal of a III-V compound semiconductor excluding nitride. A light emitting device using such an AlGaInP-based material having a large direct transition band gap can emit light with high luminance in a wavelength range of 550 to 650 nm (green to red). Applications are in progress.

FIG. 3 is a schematic sectional view showing an example of a conventional AlGaInP-based light emitting device. This conventional AlG
The aInP-based light emitting device 20 includes a first conductivity type (Al _x Ga _{1 -x} ) _0.51 In on a first conductivity type GaAs substrate 11.
_0.49 P clad layer 12 (about 1 μm thick), (Al _y Ga
_1-y ) _0.51 In _0.49 P active layer 13 (about 0.6 μm thick)
m) of the second conductivity type (Al _z Ga _{1 -z} ) _0.51 In _0.49 P
A cladding layer 14 (about 1 μm in thickness) and a current diffusion layer 25 of the second conductivity type (thickness of several μm or more) are sequentially laminated, and the upper electrode 16 and the GaAs substrate 11 are formed on the p-type current diffusion layer 25. The lower electrode 17 is provided on the lower surface.

Here, (Al _y Ga _{1 -y} ) _0.51 In _0.49
A P active layer 13 and two AlGaInP cladding layers having a bandgap larger than the active layer
Conductive type (Al _x Ga _{1 -x} ) _0.51 In _0.49 P cladding layer 12 and second conductive type (Al _z Ga _{1 -z} ) _0.51 In _0.49 P
The double heterojunction structure constituted by the clad layer 14 constitutes the light emitting layer portion 18, and the Al composition x, y, z of each AlGaInP layer constituting the double heterojunction structure is 0 ≦.
It satisfies the relations y ≦ 0.7, y <x, y <z. Also,
The (Al _y Ga _1-y ) _0.51 In _0.49 P active layer 13 functions as a light emitting layer. In the following description, if there is no special circumstances, the above (Al _x Ga _{1 -x} ) _0.51 In
_0.49 P, (Al _y Ga _1-y ) _0.51 In _0.49 P and (Al
_z Ga _1-z ) _0.51 In _0.49 P (Al _B Ga
_1-B ) _0.51 In _0.49 P or simply AlGaInP.

In the AlGaInP-based light emitting device as described above, it is necessary to provide a current spreading layer on the light emitting layer section 18, and in particular, it is necessary to provide a current spreading layer made of a material different from AlGaInP. The reason will be described with reference to FIG. In FIG. 3, the current distribution from the upper surface electrode 16 is indicated by reference numeral 19.

In the current emission of the AlGaInP-based light-emitting device, it is desirable that the current from the upper electrode 16 be effectively diffused to the entire area of the light-emitting layer section 18, particularly to the entire area of the AlGaInP active layer 13 to emit light efficiently. For that purpose, the distance (thickness) between the upper electrode 16 and the AlGaInP active layer 13 needs to be a predetermined value or more (several μm or more).

Incidentally, an AlGaInP-based light emitting device is
Usually, as shown in FIG.
The layer 12 (thickness: about 1 μm) and the layer 13 (thickness: about 0.1 μm) of the AlGaInP system are lattice-matched with the aAs substrate 11.
6 [mu] m), a layer 14 (thickness about 1 [mu] m) (Al _B G
a _1-B ) _0.51 In _0.49 P is formed, but (Al _B Ga _1-B ) _0.51 In with a total thickness exceeding 4 μm is formed.
It is extremely difficult to form a _0.49 P layer without impairing crystallinity. Therefore, in order to effectively diffuse the current from the upper electrode 16 to the entire area of the active layer 13, the thickness between the upper electrode 16 and the active layer 13 needs to be several μm or more. The formation of a layer of this thickness is made of AlGaI
With nP-based materials, it is almost impossible for the reasons described above.

Therefore, conventionally, a layer made of a material other than AlGaInP is used as the current diffusion layer 25 to form the light emitting layer 18.
And the current from the upper surface electrode 16 is changed to AlGaInP.
It has been practiced to effectively diffuse the entire active layer 13 to obtain efficient light emission.

As a material of the current spreading layer 25, a direct band gap larger than the energy of the photon (Equation 1) is used on the assumption that the photon radiated from the AlGaInP active layer 13 is not absorbed.

[0010]

(Equation 1) Al _w Ga _{1 -w} As (0.45 ≦ w <1, usually w ≒ 0.7) or GaP having been used conventionally.

[0011]

However, the above Al _w G
When a _1-w As or GaP is used as the material of the current diffusion layer, both have a serious problem, which will be described below.

(Al _w Ga _{1 -w} As current diffusion layer) AlG
Since the light emission from the aInP active layer 13 is not absorbed by the Al _w Ga _{1 -w} As current diffusion layer 25, Al _w G having a high Al concentration and a high Al concentration (for example, w ≒ 0.7) is usually used.
a _1-w As is used. The high Al concentration Al _w
When using Ga _1-w As a material for the current diffusion layer 25, since Al _w Ga _1-w As of such high Al concentration tends very oxidized, energizing emission using the AlGaInP-based light-emitting device 20 outdoors Then, there is a problem that the luminescence of the Al _w Ga _{1 -w} As current diffusion layer 25 is deteriorated and the light emission luminance is further degraded with the oxidation. However, Al _w Ga
_Since the lattice mismatch between _1-w As and (Al _B Ga _{1 -B} ) _0.51 In _0.49 P is relatively low at about 0.1%, (Al _z G
a _{1 -z} ) _0.51 In _0.49 P clad layer 14 and Al _w Ga _{1 -w} As current diffusion layer 2 formed on clad layer 14
5 and a good crystal interface is formed,
This has the advantage that an Al _w Ga _{1 -w} As current spreading layer having good crystal quality can be obtained.

(GaP Current Diffusion Layer) GaP is (Al _B G
a _1-B ) The lattice mismatch with _0.51 In _0.49 P, which is as high as about 4%, makes crystal growth of GaP on the (Al _z Ga _{1 -z} ) _0.51 In _0.49 P cladding layer 14 extremely difficult. It is. Further, when the lattice mismatch rate is about 4%, dislocations of about 1 × 10 ¹² cm ⁻² occur at the interface between the cladding layer 14 and the GaP current diffusion layer 25 formed on the cladding layer 14. At the same time, local internal stress is generated at this interface. These dislocations and internal stress affect the light emitting layer portion 18, particularly the AlGaInP active layer 13 which plays a major role in light emission. For this reason, when the AlGaInP-based light emitting device 20 is used for energized light emission, there is a problem that device characteristics, particularly, emission luminance are deteriorated. However, Ga
Since P is a material that is not easily oxidized, the high Al concentration A
It has an advantage that it does not cause a problem like l _w Ga _{1 -w} As.

In view of the above, the present invention provides a current diffusion layer which has good lattice matching with (Al _B Ga _{1 -B} ) _0.51 In _0.49 P constituting the light emitting layer portion, has a current diffusion layer which is not easily oxidized, and emits light for a long period of time. It is an object of the present invention to provide a long-life and highly reliable AlGaInP-based light-emitting device that does not cause deterioration in light-emitting characteristics or the like.

[0015]

In order to solve the above problems, the present invention provides a light emitting layer portion having an AlGaInP double heterojunction structure and a current diffusion layer formed on the light emitting layer portion on a GaAs substrate. In the AlGaInP-based light emitting device, the current diffusion layer is formed of (Al
_y Ga _1-y ) _0.51 In _0.49 Direct band gap larger than the energy of photons emitted from the active layer (Equation 1)

[0016]

(Equation 1) _{Al w Ga 1-w As 1} -u P u layer and said Al _w G having
_{a 1-w As 1-u} P u GaAs 1-v formed on the layer was set to two layers of P _v layer.

The Al composition y of the (Al _y Ga _1-y ) _0.51 In _0.49 P active layer is 0 ≦ y ≦ 0.7, and the Al _{w
Ga 1-w As 1-u} P u Al composition w, P composition u and GaP mixed crystal ratio v of the GaAs _1-v P _v, respectively 0.45 ≦
Preferably, w <1, 0 <u ≦ 0.08 and 0.4 ≦ v <0.8.

The total thickness of the current diffusion layer (Al _w Ga
The sum of the thickness of the _1-w As _1-u P _u layer and the thickness of the GaAs _1-v P _v layer) is 5 μm in order to maintain the crystallinity of the light emitting layer portion and sufficiently perform the current spreading layer. Must be at least
To increase the efficiency of external emission of emitted light, the greater the thickness, the greater the efficiency.

Al _w Ga _{1 -w} As _{1 -u Pu} (where 0.
45 ≦ w <1, 0 <u ≦ 0.08), (Al _B Ga _1-B ) _0.51 In grown lattice-matched with the GaAs substrate.
_{Since the} lattice constant is very close to _0.49 P, AlGaInP
A light emitting layer portion and Al _w Ga _{1 -w} As grown on the light emitting layer portion
_A good crystal interface is formed between the Al-Ga and the _{1-u Pu} layer, and Al _w Ga _1-w As having good crystal quality is obtained.
_{A 1-u Pu} layer is obtained. In particular, by controlling the Al composition w and the P composition u (for example, Al _0.7 Ga _0.3 As _0.97
P _0.03), it is possible to perfectly lattice matched with _{(Al B Ga 1-B)} 0.51 In 0.49 P at room temperature, (Al _B Ga
_1-B ) _0.51 In _0.49 P layer and Al _w Ga _1-w As _{1-u Pu}
The internal stress caused by the difference in lattice matching with the layer can be reduced to zero. Also, GaAs _1-v P _v (where, 0.4 ≦ v <0.8) is accompanied not lattice constant changes in the composition ratio v is changed, for example, said GaAs _0.5 P _0.5 layer Al _w Ga _{When formed on the 1-w} As _{1-u Pu} layer, Al _w Ga _1-w As _{1-u Pu} and GaAs _0.5 P _0.5
Is about 2%, and a GaAsP layer having a lower dislocation density can be grown as compared with a case where GaP is directly grown as a current diffusion layer. In addition, in the current diffusion layer having a double structure according to the present invention, the interface at which dislocations occur is caused by the Al _w Ga _1-w As _{1-u Pu} layer and the GaAs _1-v P
_{Since this} is an interface with the _v- layer, the interface is Al _w Ga _{1 -w} A
s _1-u corresponding to the thickness of the P _u layer only will be spaced from the light emitting layer portion, dislocations generated in the interface is less likely to affect to the light emitting layer portion. Thereby, high crystal quality of the light emitting layer can be maintained.

Further, GaAs _1-v P _v is a material that is very unlikely to be oxidized like GaP, so that GaAs _1-v P _{v
The v} layer has the effect of serving as a protective film for preventing oxidation of the Al _w Ga _{1 -w} As _{1 -uPu} layer.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an AlGaInP light emitting device according to the present invention will be described with reference to FIGS. However, chemical formulas, elements, layer configurations, film thicknesses, relative positions thereof, and the like stored in the examples are not intended to limit the scope of the present invention to them, but are merely described, unless otherwise specified. It is only an example.

The MOVPE (metal organic chemical vapor deposition) method is used to grow each layer of the AlGaInP light emitting devices of this embodiment and the comparative example. The raw materials of Al, Ga, In, P, and As are each trimethylaluminum [Al (CH ₃ )].
₃ : TMAl], trimethylgallium [Ga (CH ₃ )]
₃ : TMGa], trimethylindium [In (C
H ₃ ) ₃ : TMIn], phosphine (PH ₃ ) and arsine (AsH ₃ ). Further, hydrogen selenide (H ₂ Se) and dimethyl zinc [Zn (CH ₃ ) ₂ : DMZn] are used as the n-type and p-type dopant sources, respectively.

FIG. 2 shows an example of the structure of a growth apparatus used for growing each layer by the MOVPE method. In the figure, the vapors of the various Group III metal organics and the hydrides of the gaseous Group V elements are mixed by selecting a partial pressure and a flow rate according to the composition of the growth, and the obtained mixed gas is mixed. It is supplied to the reaction chamber 50 and a desired growth layer is formed on an n-type or p-type GaAs substrate arranged in the reaction chamber 50. In the figure, 51 is a phosphine (P
A gas cylinder for storing gaseous hydrides such as H ₃ ) and arsine (AsH ₃ ) is supplied to a carrier gas flow path 55 such as hydrogen through a pressure / flow rate regulator 52 and a control valve 53. Reference numeral 56 denotes a bubbling tank for generating a vapor of a metal such as trimethylaluminum [TMAl], trimethylgallium [TMGa], and trimethylindium [TMIn], which is bubbled by a hydrogen gas whose pressure / flow rate is controlled by the pressure / flow rate regulator 52. The vaporized metal organic material is supplied to a carrier gas path 55 such as hydrogen through the control valve 53. The group III metal organic vapor and the group V element hydride generate a predetermined mixed gas by selecting a partial pressure and a flow rate according to the composition of the growth via the gas path 55, and The gas is supplied to the reaction chamber 50 surrounded by the heating element and adjusted to a predetermined pressure and a predetermined temperature, and a desired growth layer is formed on the n-type or p-type GaAs substrate disposed in the reaction chamber 50. Specifically, under a reduced pressure of 50 Torr, V
A gas obtained by mixing a group III element and a group III element so that the supply ratio (V / III ratio) is 100 is used as a source gas for the growth layer, and GaAs is grown at a growth temperature of 710 ° C. and a growth rate of 4 μm / hour. Each layer of the AlGaInP-based light emitting device is formed on the substrate. By converting the thus-obtained epitaxial wafer into an element, AlGaI
An nP light emitting device is obtained.

According to the manufacturing method described above, the Al
A GaInP-based light emitting device 10 was manufactured. FIG. 1 is a schematic sectional view showing one embodiment of the AlGaInP-based light emitting device of the present invention. In this figure, the same members as those in FIG. This light-emitting device 10 has n-type GaAs
On the s substrate 11, n-type (Al _0.7 Ga _0.3 ) _0.51 In
_0.49 P clad layer 12 (about 1 μm thick), (Al _0.15 G
a _0.85 ) _0.51 In _0.49 P active layer 13 (thickness: about 0.6 μm)
m), p-type (Al _0.7 Ga _0.3 ) _0.51 In _0.49 P-type cladding layer 14 (about 1 μm thick) and p-type Al _0.7 Ga _0.3 As _0.97 P _0.03 layer 15 a constituting the p-type current diffusion layer 15
(Thickness: about 3 μm), p-type GaAs _0.5 P _0.5 layer 15b
(Thickness: about 7 μm) are sequentially laminated, and the p-type GaAs is formed.
_An upper electrode 16 is provided on the _0.5P0.5 layer 15b, and a lower electrode 17 is provided on the lower surface of the n-type GaAs substrate.

(Evaluation results of various characteristics) [Table 1] shows the evaluation results of various characteristics of the AlGaInP-based light emitting device of the present example, and shows the AlGaIn of the conventional structure of Comparative Example 1 and Comparative Example 2.
This is shown in comparison with that of the P-based light emitting device. The AlGaInP-based light-emitting devices of Comparative Examples 1 and 2 are the AlGaInP-based light-emitting devices having the conventional structure shown in FIG.
_0.7 Ga _0.3 As current diffusion layer (about 10 μm) and p-type G
It is the same as the example except that an aP layer (thickness: about 10 μm) was formed.

As is clear from Table 1, the AlGaInP-based light emitting device of the present embodiment has higher light emission luminance and light emission luminance than the conventional AlGaInP light emitting devices (Comparative Examples 1 and 2). AlGaIn with almost no deterioration
This is a P-based light emitting device, and the effectiveness of the present invention has been proved. That is, when the current diffusion layer is formed only of the Al _0.7 Ga _0.3 As layer (Comparative Example 1), the light emitting layer portion is formed (Al _B
Since the lattice matching with Ga _1-B ) _0.51 In _0.49 P is good, the initial light emission luminance is as high as 100, but the current diffusion layer is easily oxidized and deteriorates due to long-term use, resulting in a poor life of 66%. On the other hand, when the current diffusion layer is formed only of GaP (Comparative Example 2), the light emitting layer portion is formed (Al _B
Since the lattice mismatch with Ga _1-B ) _0.51 In _0.49 P is high, the dislocation and internal stress existing at the interface between the light emitting layer portion and the GaP current diffusion layer affect even the AlGaInP active layer, Has a low emission luminance of 83 and a life of 8
It turns out that it is inferior to 8%. On the other hand, in the example, the initial light emission luminance is as high as 107 and the life is as good as 98%. It can be seen that the effect of the current diffusion layer composed of the two layers is remarkable.

[0027]

[Table 1]

In Table 1, the evaluation data is (10
(Epitaxial wafer) × (10 light emitting devices / epitaxial wafer) = 100 light emitting devices. In addition, luminance measurement current: 20 mA Life (other name: afterglow ratio) Afterglow ratio = (I / I ₀ ) × 100 (%) I ₀ : initial luminance I: 85 ° C., 85% DC, 50 mA DC This is the luminance after 1000 hours of energized light emission.

[0029]

As described above, according to the present invention,
(Al _B Ga _1-B ) _0.51 In _0.49 P which constitutes the light emitting layer portion
Al _w Ga _1-w As _{1-u Pu} layer (0.45 ≦ w <1, 0 <u ≦ 0.08) having good lattice matching with Al _w Ga _1-w As _{1- A} GaAs _1-v P _v layer formed on the _u P _u layer which is difficult to be oxidized (provided that 0.4 ≦ v <0.
8) By providing the two-layer current diffusion layer, a long-life and highly reliable AlGaInP-based light-emitting device that does not cause deterioration in light-emitting characteristics even when the light emission is used for a long time can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional explanatory view showing one embodiment of an AlGaInP-based light emitting device of the present invention.

FIG. 2 is a schematic explanatory view showing an example of a manufacturing apparatus used when growing each layer by the MOVPE method.

FIG. 3 shows a conventional AlGaInP-based light emitting device (Comparative Example 1,
FIG. 4 is a schematic sectional explanatory view showing one example of Comparative Example 2 and General Example).

[Explanation of symbols]

Reference Signs List 10 AlGaInP-based light-emitting device according to embodiment of the present invention 11 GaAs substrate 12 clad layer 13 active layer 14 clad layer 15 Current diffusion layer of AlGaInP-based light-emitting device according to embodiment of the present invention 15a AlGaAsP layer 15b GaAsP layer 16 Top electrode 17 Lower electrode 18 Light emitting layer (double hetero junction structure) 19 Current distribution 20 Conventional AlGaInP light emitting device 25 Current diffusion layer of conventional AlGaInP light emitting device

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-342936 (JP, A) JP-A-6-326360 (JP, A) JP-A 8-172218 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H01L 33/00 JICST file

Claims (5)

(57) [Claims] 1. An AlGaInP-based light emitting device having a light emitting layer portion having an AlGaInP double heterojunction structure on a GaAs substrate and a current spreading layer formed on the light emitting layer portion, wherein the current spreading layer is a light emitting layer. Part of (Al _y Ga _1-y )
_0.51 In _0.49 Direct band gap larger than the energy of photons emitted from the P active layer ([Equation 1]) _{Al w Ga 1-w As 1} -u P u layer and said Al _w G having
An AlGaInP-based light-emitting device comprising two layers of a GaAs _1-v P _v layer formed on an a _1-w As _{1-u Pu} layer. 2. The (Al _y Ga _1-y ) _0.51 In _0.49 P
2. The AlGaIn according to claim 1, wherein the Al composition y of the active layer is 0 ≦ y ≦ 0.7.
P-based light emitting device. Wherein Al of the _{Al w Ga 1-w As 1} -u P u
3. The AlGaInP-based light emitting device according to claim 1, wherein the composition w and the P composition u satisfy 0.45 ≦ w <10 <u ≦ 0.08. Wherein said GaAs _1-v P _v of the GaP mixed crystal ratio v
4. The AlGaInP-based light emitting device according to claim 1, wherein 0.4 ≦ v <0.8. 5. The AlGaInP-based light emitting device according to claim 1, wherein a total thickness of the current diffusion layer is 5 μm or more.