JP3193087B2 - AlGaInP 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 an AlGaInP semiconductor light emitting device, and more particularly to an AlGaInP red semiconductor laser device operating at a low threshold or a light emitting diode device having a high luminous efficiency.

[0002]

2. Description of the Related Art In recent years, with the practical use of semiconductor laser devices having the advantages of small size, high output, and constant price, the application of lasers to general industrial machines and consumer machines, for which use of laser light sources has been difficult in the past, has been advanced. I have. Above all, there has been remarkable progress in fields such as optical disk devices and optical communication. In the future, semiconductor laser devices are expected to be applied to more fields.

A semiconductor light emitting device using an AlGaInP crystal is
100 more than conventional semiconductor laser device using AlGaAs crystal
It has an emission wavelength band on the shorter wavelength side than nm. For example, in the case of a semi-moving body laser device, the recording density of an optical disc or the like is improved,
Since it has characteristics that can be used as a substitute for -Ne lasers, research is proceeding toward its practical use.

FIG. 3 shows an example of a conventional semiconductor laser device using an AlGaInP-based crystal. This semiconductor laser device has a double hetero structure in which an active layer 35 having a higher refractive index than these clad layers is formed between two different clad layers 33 and 39. In the double hetero structure, the refractive index of the active layer 35 needs to be larger than the refractive indexes of the two cladding layers 33 and 39 in order to form an optical waveguide and efficiently confine light in the active layer 35.

In this semiconductor laser device, an n-type GaAs buffer layer 32, n
The type GaAs substrate 31 and the electrode 314 are sequentially laminated. On the surface side of the p-type AlGaInP cladding layer 39, n-type GaAs
Current constriction layer 312, p-type GaInP intermediate layer 310, p-type GaAs
A contact layer 311 and an electrode 313 are sequentially stacked. The p-type GaInP intermediate layer 310 and the p-type GaAs contact layer 311 are formed at the center by etching, and the n-type GaAs current narrowing layer 312 is laminated on the outer periphery.

In such a double hetero structure, the inside of the active layer 35, and the active layer 35 and the barrier layer 33, which increase the threshold value or decrease the reliability of the semiconductor laser,
The non-emission annihilation process of the carrier at the interface 39 can be quantitatively determined by the non-emission lifetime τ _nr of the carrier (hole) represented by the following formula. That is, when τ _nr is short, carriers (holes) are _largely eliminated in the non-light emitting process, and do not contribute to light emission.

1 / τ _nr = 1 / τ _nra + S / d where τ _nra is the non-light-emitting lifetime of carriers inside the active layer 35, and S is the interface between the active layer 35 and the barrier layers 33 and 39. And d represents the thickness of the active layer.

Generally, when the active layer 35 is made of a crystalline material containing no Al, as in the above example, the GaInP active layer 3
5 itself has a very small non-radiative extinction,
τ _nra can be ignored. Therefore, the non-emission process of carriers is governed by the non-emission recombination process at the interface between the active layer 35 and the barrier layers 33 and 39.

Further, when d becomes very small as in the quantum well active layer, as apparent from the above equation, the influence of the non-light emitting process particularly at the interface becomes large. Therefore, in the semiconductor light emitting device, it is important to improve the interface between the active layer 35 and the barrier layers 33 and 39 in order to improve the characteristics.

As a method of reducing the interface recombination, for example, a superlattice buffer layer 3 made of GaInP / AlGaInP is used.
A method of growing the active layer 35 immediately after the barrier layer 33 on the rear surface side and growing the active layer 35 immediately after that is known in the molecular beam crystal growth method.

[0011]

As described above, when the superlattice buffer layer 32 is grown by, for example, a molecular beam crystal growth method, it is necessary to frequently open and close the cell shutter, which causes a failure of the crystal growth apparatus. Can be a factor.

A high-temperature crystal growth, which is known as a method of growing a high-quality AlGaAs crystal using an AlGaAs-based material, is as follows.
In growing AlGaInP crystals, P, Ga, In
Re-evaporation occurs, and in this crystal system, it is necessary to control the growth conditions such as the growth temperature with extremely high precision.

The present invention has been made in order to solve such disadvantages of the prior art, and has as its object the purpose of GaInP.
An object of the present invention is to improve the quality of the interface between the active layer and the barrier layer and improve the reliability of the AlGaInP-based semiconductor light emitting device.

[0014]

The AlGaInP of the present invention
The semiconductor light emitting device includes an active layer made of Ga _x In _1-x P,
Ga is interposed between barrier layers made of Ga _y In _1-y P which have a mixed crystal ratio of Ga larger than that of the active layer and satisfy the condition of x <y .
The barrier layer sandwiching the active layer is composed of AlGaInP
Double heterostructure sandwiched between the clad layers
It is characterized by doing .

Preferably, the active layer is formed of GaInP having a composition ratio lattice-matched to a GaAs substrate. Further, a GaInP crystal which is usually made of GaAs and lattice-matched to the substrate is x = 0.
It becomes 51. As described above, by sandwiching the active layer with Ga _x In _1-x P crystals having a mixed crystal ratio of x = 0.75 or more, a double hetero junction capable of confining carriers can be formed. In a GaInP crystal with x> 0.51, the lattice constant is smaller than that of the active layer (x = 0.51). x =
With 0.75 GaInP, the lattice mismatch rate with Ga _0.51 In _0.49 P becomes about 1.5%.

Therefore, when this layer is inserted as a barrier layer into a crystal layer of a lattice matching system with the GaAs layer, the layer thickness must be equal to or less than the critical film thickness so that misfit transition due to strain breakdown does not occur. is there. For example, GaIn of x = 0.75
In the case of a P layer, it is considered necessary to set the thickness to about 10 nm or less. At this time, if the thickness of the barrier layer is reduced, carriers penetrate the barrier layer due to a so-called tunneling phenomenon and escape from the active layer. According to the analysis result of the tunneling probability, tunneling can be prevented if there is a barrier layer of about 10 nm.

[0017]

In the AlGaInP semiconductor light emitting device of the present invention, the quality of the interface between the active layer and the AlGaInP barrier layer is improved by inserting a GaInP crystal containing no Al between the active layer and the AlGaInP barrier layer. Therefore, the reliability of the AlGaInP-based semiconductor light emitting device becomes higher, and the efficiency becomes higher.

[0018]

Embodiments of the present invention will be described below.

FIG. 1 shows an embodiment of an AlGaInP semiconductor light emitting device according to the present invention. This AlGaInP semiconductor light emitting device has a double hetero structure as shown in the figure. This double hetero structure has a Ga _0.51 In _0.49 P active layer 15 (80 nm thick) located substantially at the center and an n layer laminated on the back side thereof.
-Type Ga _0.75 In _0.25 P barrier layer 14 (10 nm thick) and p-type Ga _0.75 In _0.25 P barrier layer 1 laminated on the surface side
6 (10 nm thick). N-type Ga _0.75 In _0.25 P barrier layer 14 as a GaInP barrier layer and p-type Ga
The mixed crystal ratio of Ga in the _0.75 In _0.25 P barrier layer 16 is larger than the mixed crystal ratio of Ga in the Ga _0.51 In _0.49 P active layer 15 which is the GaInP active layer. That is, the condition x <y is satisfied. In the double hetero structure, the refractive index of the active layer must be larger than that of the cladding layer in order to form an optical waveguide and efficiently confine the light in the active layer. It needs to be smaller.

Further, an n-type Ga _0.75 In _0.25 P barrier layer 14
N-type (Al _0.7 Ga _0.3 ) _0.51 In _0.49 P
A cladding layer 13 (1.0 μm thick), an n-type GaAs buffer layer 12, an n-type GaAs substrate 11, and an Au-Ge-Ni electrode 114 are sequentially stacked.

The p-type Ga _0.75 In _0.25 P barrier layer 16
P-type (Al _0.7 Ga _0.3 ) _0.51 In _0.49 P
Cladding layer 17 (thickness 0.3 nm), Ga _0.51 In _0.49 P
Etching stop layer 18 (8 nm thick), p-type (Al
_0.7 Ga _0.3 ) _0.51 In _0.49 P cladding layer 19 (thickness: _0.7 Ga _0.3 )
5 μm), a p-type Ga _0.51 In _0.49 P intermediate layer 110 (thickness: 50 nm), a p-type GaAs contact layer 111, an n-type GaAs current constriction layer 112, and an Au-Zn electrode 113.

Incidentally, p-type (Al _0.7 Ga _0.3 ) _0.51 In
_{The 0.49} P cladding layer 19, the p-type Ga _0.51 In _0.49 P intermediate layer 110, and the p-type GaAs contact layer 111 are formed in the center by etching, and the n-type GaAs current constriction layer 112 is laminated on the outer periphery.

Each of the above crystal layers is formed, for example, by a molecular beam crystal growth method. After a silicon oxide film is formed on the surface of the growth wafer by sputtering, the upper layers 19, 110, and 111 are removed by etching using the silicon oxide film as a mask. The n-type GaAs current constriction layer 112 is regrown thereon by, for example, a molecular beam crystal growth method, and then the n-type GaAs current constriction layer 112 grown on the mesa is removed together with the silicon oxide film. Finally, Au-Zn electrode 113 on the surface,
If the Au-Ge-Ni electrode 114 is formed on the back surface,
An AlGaInP-based semiconductor laser device can be manufactured.

By measuring the surface and cross section of the grown wafer by electron microscopic observation and X-ray analysis, it was confirmed that a good crystal film free from dislocation defects was grown.
In addition, the characteristics of the semiconductor laser were particularly improved at a low threshold value as well as the conventional one.

FIG. 2 shows another embodiment of the AlGaInP semiconductor light emitting device of the present invention. This AlGaInP semiconductor light emitting device is an example of an edge-emitting light emitting diode device, and has a double hetero structure as in the first embodiment. This double hetero structure has a Ga _0.45 In _0.55 P active layer 25 (thickness 10 nm) located substantially at the center, an n-type Ga _0.75 In _0.25 P barrier layer 24 (10 nm thick) laminated on the back side thereof, A p-type Ga _0.75 In _0.25 P barrier layer 26 laminated on the surface side
(Thickness: 10 nm). In this double hetero structure, n-type Ga _0.75 In _0.25 which is a GaInP barrier layer
The mixed crystal ratio of Ga in the P barrier layer 24 and the p-type Ga _0.75 In _0.25 P barrier layer 26 is Ga _0.45 In _0.55 which is a GaInP active layer.
It is larger than the Ga mixed crystal ratio of the P active layer 25.

Further, on the back side of the Ga _0.75 In _0.25 P barrier layer 24, an n-type (Al _0.7 Ga _0.3 ) _0.51 In _0.49 P cladding layer 23 (1.0 μm in thickness), an n-type GaAs substrate 21, and an Au-
Ge-Ni electrodes 214 are sequentially stacked.

On the surface side of the Ga _0.75 In _0.25 P barrier layer 26, a p-type (Al _0.7 Ga _0.3 ) _0.51 In _0.49 P cladding layer 29 (1.0 μm in thickness) and a Ga _0.51 In _0.49 P intermediate layer 210 are provided. (Thickness: 50 nm), p-type GaAs contact layer 21
1. Au-Zn electrodes 213 are sequentially stacked.

The Ga _0.45 In _0.55 P active layer 25 has an x composition of a lattice mismatching system, where x <0.51. The emission wavelength is about 680 nm mainly due to the effect of reduction of band gap energy. Lattice-matched Ga _0.45 In _0.55 P
It is longer than the active layer 25.

In the above embodiment, the case where the molecular beam crystal growth method is used as the crystal growth method has been described. However, it goes without saying that the AlGaInP semiconductor light emitting device of the present invention does not depend on the crystal growth method. Also, for example, Ga
In _0.45 an In _0.55 P active layer 25 is a quantum well, in separate confinement heterostructure composed of carrier confinement layers sandwiching the, Ga _0.45 In _0.55 P active layer of the present invention on both sides of the active layer as part of a separate confinement layer The same effect can be expected even if 25 is used.

[0030]

According to the AlGaInP semiconductor light emitting device of the present invention,
It has a double hetero structure in which an active layer made of Ga _x In _1-x P is sandwiched between barrier layers made of Ga _y In _1-y P having a mixed crystal ratio of Ga larger than that of the active layer. By inserting a GaInP crystal containing no Al between the active layer and the AlGaInP barrier layer, the quality of the interface between the active layer and the AlGaInP barrier layer is improved. Thereby, a highly reliable, highly efficient or low threshold AlGaInP-based semiconductor light emitting device can be provided.

According to the second aspect of the present invention, since the active layer is made of GaInP having a composition ratio lattice-matched to the GaAs substrate, even in a semiconductor light emitting device having a relatively thick active layer, the quality due to strain can be improved. The present invention can be applied without causing deterioration.

[Brief description of the drawings]

FIG. 1 is a sectional view of an AlGaInP-based semiconductor laser device according to one embodiment of the present invention.

FIG. 2 is a sectional view showing another embodiment of the AlGaInP-based semiconductor laser device.

FIG. 3 is a cross-sectional view showing an example of a conventional semiconductor laser device using an AlGaInP-based crystal.

[Explanation of symbols]

11, 21 n-type GaAs substrate 12 n-type GaAs buffer layer 13, 23 n-type (Al _0.7 Ga _0.3 ) _0.51 In _0.49
P cladding layer 14, 24 n-type Ga _0.75 In _0.25 P barrier layer 15, 25 Ga _0.45 In _0.55 P active layer 16, 26 Ga _0.75 In _0.25 P barrier layer 17 p-type (Al _0.7 Ga _0.3 ) _0.51 In _0.49
P cladding layer 18 Ga _0.51 In _0.49 P etching stop layer 19, 29 p-type (Al _0.7 Ga _0.3 ) _0.51 In _0.49
P cladding layer 110, 210 p-type Ga _0.51 In _0.49 P intermediate layer 111, 211 p-type GaAs contact layer 112, n-type GaAs current constriction layer 113, 213 Au-Zn electrode 114, 214 Au-Ge-Ni electrode

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Atsushi Tsunoda 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Kentaro Tani 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp shares In-company (56) References JP-A-3-265183 (JP, A) JP-A-2-310985 (JP, A) JP-A-61-271888 (JP, A) JP-A-5-63291 (JP, A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01S 5/00-5/50 H01L 33/00

Claims (4)

(57) [Claims] 1. An active layer comprising Ga _x In _1-x P is formed by
Is larger than that of the active layer and satisfies the condition of x <y.
with sandwiched by barrier layers formed of a _y In _1-y P, activity
The barrier layer sandwiching the layer is made of AlGaInP.
Has a double hetero structure sandwiched between clad layers
An AlGaInP semiconductor light emitting device, comprising: 2. The AlGaInP semiconductor light emitting device according to claim 1, wherein said active layer is formed of GaInP having a composition ratio lattice-matched to a GaAs substrate. 3. The barrier layer according to claim 1, wherein Ga _y In _1-y P is 0.6.
The AlGaInP half according to claim 1, which satisfies <y <1.
Conductive light emitting device. (4) The thickness of the barrier layer causes crystal breakage
Tunneling can be prevented below the critical film thickness
2. The AlGaInP semiconductor according to claim 1, which is not less than a thickness.
Light emitting device.