JPH0645698A - Semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To suppress diffusion of impurity in an active layer even when a clad layer is doped in a high concentration by providing a low concentration doping region of the side near the active layer and a high concentration doping region of the farther side at both or one of a first conductivity type clad layer and a second conductivity type clad layer. CONSTITUTION:Upper and lower clad layers for holding an active layer 14 are formed of clad layers 13, 15 low concentration doped at the side near the layer 14, and clad layers 12, 16 high concentration doped at the side farther from the layer 14. The layers 12, 16 are high impurity concentrations, but since the layers 13, 15 low concentration doped exist to the layer 14, a decrease in quality of the layer 14 due to impurity diffusion does not occur. The layers 12, 16 occupy most of the n-type clad layer and the p-type clad layer to improve carrier confining effect of the clad layer and to realize a decrease in the resistance of the clad layer.

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.

[0002]

2. Description of the Related Art Currently, a semiconductor light emitting device having an AlGaInP-based double hetero structure having GaInP or AlGaInP as an active layer is mainly developed as a visible light semiconductor laser. In such a visible light semiconductor laser, it is possible to improve the effect of confining carriers and reduce the resistance of the cladding layer by doping the cladding layer with a high concentration of impurities, and as a result, to improve the characteristics of the semiconductor laser. Can be planned.

[0003]

However, in the structure of the conventional visible light semiconductor laser, the active layer and the clad layer are in direct contact with each other. Therefore, when the clad layer is heavily doped, heating during the laser manufacturing process, etc. There is a problem that the doped impurities diffuse from the clad layer to the active layer, resulting in deterioration of the crystal quality of the active layer and change of the band gap. Among other things
This was remarkable when the p-type cladding layer was heavily doped.

Further, in the conventional structure having a striped ridge on the crystal surface, in the second conductivity type cladding layer,
High-concentration doping reduces the resistance of the cladding layer,
Since the current easily flows in the direction parallel to the GaAs substrate surface, the current spreads in the second conductivity type clad layer, and there is a problem that the effective current confinement effect in the active layer is weakened.

The present invention solves such a conventional problem, and provides a semiconductor light emitting device which realizes high-concentration doping in a cladding layer and at the same time suppresses diffusion of impurities into an active layer. The purpose is.

[0006]

In order to achieve the above object, the present invention provides a low-concentration layer in which both or one of the first-conductivity-type cladding layer and the second-conductivity-type cladding layer is closer to the active layer. A doping region and a high-concentration doping region on the side far from the active layer are provided.

[0007]

According to the present invention, since the impurity concentration of the clad layer on the side close to the active layer is suppressed to a low level by the above structure, the diffusion of impurities from the clad layer to the active layer can be reduced and the entire clad layer can be reduced. As a result, since high-concentration doping is realized, the characteristics of the semiconductor laser can be improved.

[0008]

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a cross section of a visible light semiconductor laser, in which the first conductivity type cladding layer is an n-type cladding layer and the second conductivity type cladding layer is a p-type cladding layer.

In FIG. 1, 10 is an n-type GaAs substrate,
11 is an n-type GaAs buffer layer, 12 is a heavily doped n-type cladding layer, 13 is a lightly doped n-type cladding layer, 14 is an active layer, 15 is a lightly doped p-type cladding layer, and 16 is a high density. Doped p
Is a p-type GaAs cap layer, 18 is an n-electrode, and 19 is a p-electrode.

The active layer 14 is lattice-matched with GaAs within a range of ± 1% to form (Al _x Ga _1-x ) _y In _1-y P (0
≦ x ≦ 1) consists, n-type cladding layer 12, 13 and p-type cladding layer 15, 16, and lattice-matched within a range of ± 1% in _{GaAs, (Al x 'Ga 1} -x') y _' In _1-y' P
The one consisting of (0 ≦ x ′ ≦ 1) is used.

In this embodiment, both the heavily doped n-type cladding layer 12 and the heavily doped p-type cladding layer 16 have a thickness of 0.8 μm and a doping concentration of 1 × 10 ¹⁸ cm ⁻³ or more. On the other hand, both the lightly doped n-type cladding layer 13 and the lightly doped p-type cladding layer 15 have a thickness of 0.1 μm and a doping concentration of 5 × 10 ¹⁷ cm ⁻³ .

In the semiconductor laser configured as described above, the upper and lower clad layers sandwiching the active layer 14 are the active layer 1
Lightly doped cladding layers 13, 1 on the side close to 4
5 and the highly-doped clad layers 12 and 16 on the side far from the active layer 14, and the lightly-doped clad layers 13 and 15 are adjacent to the active layer 14,
The diffusion of the doped impurities into the active layer 14 can be ignored.

A highly doped clad layer 1
Nos. 2 and 16 have high impurity concentrations, but since the lightly doped clad layers 13 and 15 are present between them and the active layer 14, respectively, the quality of the active layer 14 due to the diffusion of impurities is reduced. No decrease occurs. At this time, the heavily-doped clad layers 12 and 16 are mostly the n-type clad layer and the p-type clad layer (approximately 89
%), It is possible to improve the effect of confining carriers in the cladding layer and reduce the resistance of the cladding layer as a whole.

The thickness of the lightly doped cladding layers 13 and 15 can be set arbitrarily within a range where diffusion of the doped impurities can be ignored, but in order to improve laser characteristics, the thickness is as thin as possible. It is desirable to be 0.1 μm or more in practice. In addition, the highly doped cladding layers 12 and 16
It is desirable that the concentration difference between the lightly doped cladding layers 13 and 15 is twice or more.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 shows a cross section of a visible light semiconductor laser, in which the first conductivity type cladding layer is an n-type cladding layer and the second conductivity type cladding layer is a p-type cladding layer.

In FIG. 2, 20 is an n-type GaAs substrate,
21 is an n-type GaAs buffer layer, 22 is a heavily doped n-type cladding layer, 23 is a lightly doped n-type cladding layer, 24 is an active layer, 25 is a p-type lightly doped p-type cladding layer, and 26 is p-type doped stop layer, 27 highly doped p-type cladding layer, 28 p-type GaAs cap layer, 29 n-type GaA
s block layer, 30 is a p-type GaAs contact layer, 31
Is an n electrode and 32 is a p electrode.

In this embodiment, a ridge structure is formed in a double hetero structure.
Structure is formed, and as in the first embodiment,
N-type clad layer 23 and low concentration doping
The p-type clad layer 25 is 0.1 μm thick,
Carrier concentration 5 × 10¹⁷cm ^-3Is formed so that
It In addition, in order to facilitate the formation of the ridge structure, a low concentration
Heavily doped p-type cladding layer 25 and high-concentration doping
Between the p-type clad layers 27 that have been doped
The stop layer 26 is provided.

The procedure for manufacturing the semiconductor laser of this embodiment will be briefly described below. First, the n-type GaAa substrate 20
After growing the n-type GaAs buffer layer 21 to the p-type GaAs cap layer 28 on the upper surface by the usual method, p
A resist layer is formed on the type GaAs cap layer 28, exposed, developed and removed to form a mask, and then the p-type doped stop layer 26 is removed by etching to form a ridge structure. Then, n-type Ga is formed on the crystal surface.
After growing the As block layer 29, the mask is removed, and finally the p-type GaAs contact layer 30 is grown, and the p electrode 32 is formed thereon.

By adopting the structure of this embodiment, impurities from the heavily doped n-type clad layer 22 and the heavily doped p-type clad layer 27 as described in the first embodiment to the active layer 24 are obtained. Diffusion can be suppressed, and highly-doped p except for the ridge
Since the type clad layer 27 is removed, it is possible to suppress the spread of current in the highly doped p-type clad layer 27. Therefore, in this embodiment, the effect of confining carriers in the cladding layer can be further improved as compared with the first embodiment.

In each of the above-mentioned embodiments, the low-concentration doping region and the high-concentration doping region are provided in each of the clad layers on both sides of the active layer. A lightly doped region and a heavily doped region can be provided in only one of them.

[0021]

As is apparent from the above-described embodiments, the present invention provides a low-concentration doping region on the side close to the active layer in either or both of the first-conductivity-type cladding layer and the second-conductivity-type cladding layer. Since the high-concentration doping region on the far side is provided in the active layer, diffusion of impurities from the clad layer to the active layer can be suppressed even when high-concentration doping is performed in other regions of the clad layer. Since high-concentration doping is realized in the entire clad layer, it is possible to reduce the resistance of the clad layer and improve the effect of confining carriers.

[Brief description of drawings]

FIG. 1 is a sectional view of a semiconductor laser according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a semiconductor laser according to a second embodiment of the present invention.

[Explanation of symbols]

 10 n-type GaAs substrate 11 n-type GaAs buffer layer 12 heavily doped n-type cladding layer 13 lightly-doped n-type cladding layer 14 active layer 15 lightly-doped p-type cladding layer 16 highly-doped p-type cladding layer 17 p-type GaAs cap layer 18 n-electrode 19 p-electrode 20 n-type GaAs substrate 21 n-type GaAs buffer layer 22 heavily doped n-type cladding layer 23 lightly-doped n-type cladding layer 24 active layer 25 lightly-doped p -Type clad layer 26 p-type stop layer 27 highly-doped p-type clad layer 28 p-type GaAs cap layer 29 n-type GaAs block layer 30 p-type GaAs contact layer 31 n-electrode 32 p-electrode

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masato Nakajima 3-10-1 Higashisanda, Tama-ku, Kawasaki-shi, Kanagawa Matsushita Giken Co., Ltd.

Claims (3)

[Claims] 1. An AlGa film on a GaAs substrate of the first conductivity type.
The active layer made of InP is sandwiched between a first conductive type clad layer made of AlGaInP and a second conductive type clad layer having an energy gap larger than that of the active layer, and has a double hetero structure. A semiconductor light emitting device, wherein one or both of the layer and the second-conductivity-type cladding layer have a low-concentration doping region on the side closer to the active layer and a high-concentration doping region on the side far from the active layer. 2. The active layer is within ± 1% of GaAs.
Lattice matching, (Al _xGa_1-x)_yIn_1-yP (0 ≤
x ≦ 1), the first conductivity type cladding layer and the second conductive type
The electric cladding layer is lattice-adjusted to GaAs within ± 1%.
Combined, (Al _{x '}Ga_{1-x '})_{y '}In_{1-y '}P (0 ≦ x ′ ≦
The semiconductor light emitting device according to claim 1, which comprises 1). 3. A structure having a stripe-shaped ridge on the crystal surface and removing at least the portion other than the ridge from the crystal surface to the high-concentration doping region in the second conductivity type cladding layer above the active layer. Item 3. The semiconductor light emitting device according to item 1 or 2.