JPH0637393A - Internal constriction type semiconductor laser device and its manufacture - Google Patents

Abstract

PURPOSE:To improve the controllability of a trench width and avoid damages caused by dry-etching by a method wherein an etching stop layer and first and second layers having different thicknesses are built up on a double-hetero junction and a current constitution layer having lattice matching with the etching stop is provided. CONSTITUTION:The surface part of an n-type GaAs substrate 1 is doped to provide a cladding layer 2 and an active layer 3 is built up to form a double- hetero junction part. A p-type cladding layer 4 is built up on the double-hetero junction part and an etching stop layer 13 is built up for lattice matching. A current blocking layer which has lattice matching with the etching stop layer 13 and has a stripe-shaped current injection part A is provided on the etching stop layer. The current blocking layer is composed of a first layer 14a and a second layer 14b. The respective parts of the first layer 14a and the second layer 14b are removed to form a stripe trench and a contact layer 6 is built up and the current injection part is formed by lattice matching to form an internal constitution type semiconductor laser. With this constitution, the influences of damages produced in a patterning process can be avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of an internal confinement type semiconductor laser device.

[0002]

2. Description of the Related Art Among commercially available semiconductor lasers, an InGaAlP internal confinement type semiconductor laser device is known, which will be described with reference to FIGS.

On the n-GaAs substrate 1, n-In _0.5 (G a 0.3) is formed by a metal organic chemical vapor deposition method (hereinafter referred to as MOCVD method) _.
Al _0.7 ) P 2 to p-GaAs contact layer 6 are sequentially deposited. Each will be described below. n-GaAs substrate 1 is Si
The 3 × 10 ^{1 8} cm as an impurity ^- which contain ^3, n
The type clad layer 2 is n-In _0.5 (G a _0.3 Al _0.7 )
_{. 0} 5 × 10 ¹ Si as an impurity in the composition of the ₅ P ⁷ cm ^{- 3}
The content is 1.0 μm. The active layer 3 of undoped are compositions with a thickness 0.08μm is _{In 0. 5 Ga 0. 5} P, p -type composition of the cladding layer 4 is _{P-In 0. 5 (G} a 0. 3 Al
_{. 0 7)} thickness at P 1.0 [mu] m and Zn and 5 × 10 ^{1 7} cm ^{- 3}
The composition of the current blocking layer 5 contained and superposed on this is n-Ga
_{. 0 7} Al _{0 3} As, a ^{Zn 5 × 10 1 7 cm -} . 3 contains. The contact layer 6 (see FIG. 4) has a composition of p-GaAs, is doped with 1 × 10 ¹⁹ cm ⁻³ of Zn, and has a thickness of 5.0.
In addition, a p-type electrode 7 and an n-type electrode 8 (see FIG. 4) are provided on the uppermost layer and the lowermost layer to form an InGaAlP internal constriction type semiconductor laser device 9. MOCV like this
In order to process each layer for the InGaAlP internal confinement type semiconductor laser device 9, which is lattice-matched with each other by the D method, in particular, the current blocking layer 5, n-Ga is processed by a known photolithography method.
_{0. 7} Al _{0. 3} etching mask 1 in the current blocking layer 5 made of As comprises a window 10 W ₀ stripe (elongated) shape
1 is installed (see FIG. 2). By photolithography _{Next, n-Ga 0. 7 Al} 0. Current blocking layer 5 made of ₃ As
Some of, P-In ₀ through its _{thickness. 5 (G a 0. 3} Al
_0.7 ) It is removed by a sulfuric acid-based etching solution until it reaches the surface of the p-type cladding layer 4 composed of P.

As a result, the stripe-shaped groove 12 is formed immediately below the etching mask 11 having the window 10, the etching mask 11 is removed, and the adjacent current blocking layer 5 and p-type cladding layer are again formed by the MOCVD method. A contact layer 6 of p-GaAs lattice-matched with a part of 4 is deposited. As a result, the contact layer 6 is embedded in the stripe-shaped groove 12 to form the current injection portion A (see FIG. 4).

Finally, as shown in FIG. 4, the p-type electrode 7 and the n-type electrode 8 are formed to complete the InGaAlP internal confinement type semiconductor laser device 9.

[0006]

The formation of the stripe-shaped groove 12 for the current injection portion A is carried out by isotropic etching in which the material to be treated is immersed in a sulfuric acid-based etching liquid stirred at a constant speed for a certain time. Due to the temperature distribution of the sulfuric acid-based etching liquid and the difference in the flow rate between the upstream and downstream of the sulfuric acid-based etching liquid, there is a difference in the etching rate (Etching Rate) for the material to be processed, and the etching amount depends on the position of the material to be processed. Because it is different, it varies.

Further, isotropic etching is carried out by a chemical reaction between a material to be treated and an etching liquid, so that the shape after etching is affected by the anisotropy of etching due to the crystal plane orientation. For this reason, as clearly shown in FIG. 3, it is difficult to control the width because the reaction proceeds not only in the downward direction W ₀ of the window 10 of the etching mask 11 but also in the lateral direction. That is, the groove 12 formed by isotropic etching on a 2-inch semiconductor wafer as a material to be processed has a thickness of 5.2 ± 5
There was a variation of about 0.5 μm.

Since the width W (see FIG. 3) of the groove 12 for the current injection portion A is an important parameter relating to the electrical and optical characteristics of the semiconductor laser, its variation leads to the variation of the semiconductor laser characteristics.

FIG. 5 shows a cross-sectional view after treatment by reactive ion etching (hereinafter referred to as RIE method) instead of isotropic etching. Under the physical etching conditions of the ions colliding with the surface of the material to be processed, the etching progresses only in the incident direction of the ions, that is, in the downward direction, and hardly progresses in the lateral direction, so that the controllability of the groove width is good. However, the B region, which is the periphery of the portion removed by anisotropic etching, is damaged by the collision ions, and the crystal quality of the lower portion of the groove 12, which is the current injection portion, deteriorates.

The present invention has been made under such circumstances, and it is an object of the present invention to improve the controllability of the groove width and avoid damage due to dry etching.

[0011]

_. A GaAs substrate [Means for Solving the Problems], an In ₀ to and lattice matching overlaid on the substrate _{5 (G a 1 - W Al} W)
_0.5 P Active layer and In _0.5 (G a _1-Y Al _Y ) _0.5 P
_{. (1 ≧ y> w ≧} 0) and a double heterojunction consisting of the cladding layer, an In ₀ to Cascade and lattice-matched to the double heterojunction portion _{5. (G a 1 - U} Al U) 0 5 P (0 ≧ u> 0.3), a current blocking layer having a stripe-shaped current injection portion that overlaps with this etching stop layer and is lattice-matched, and a current blocking portion and a current blocking layer ; and a contact layer matching, in order the current blocking layer from the side close to the GaAs _{substrate, in 0 5.. (G} a 1 - X Al X) 0 first layer consisting of ₅ P and G a _{1 - An} internal constriction type semiconductor laser device according to the present invention, which comprises a second layer made of _Z Al _Z As (0 ≦ Z ≦ 1), and a part of the first layer and the second layer is formed in a stripe shape in a current injection portion. There is a feature of.

Further, a method of manufacturing an internal confinement type semiconductor laser device is also characterized in that a part of the second layer is removed by a dry etching method and a part of the first layer is removed by a chemical containing phosphoric acid.

[0013]

The internal constriction type semiconductor laser device according to the present invention has an In 0.5 (G) between the double heterojunction portion and the current blocking layer _{.
a 1 -. U Al U)} 0 5 the etching stop layer is provided which consists of P (0 ≧ u> 0.3) , a two-layer structure comprising a current blocking layer from the first layer and the second layer. By forming the etching stop layer, the influence of damage caused in the patterning process of this two-layer structure is prevented.

In forming the groove necessary for forming the current injection portion, the second layer is processed by an anisotropic etching process so that the etching in the lateral direction (direction along the main surface of the substrate) is eliminated and the thickness is increased. The thin first layer is isotropically etched to prevent deterioration of characteristics as a laser device. As a result, the controllability of the groove width is improved, the crystal in the current injection layer is prevented from being damaged by the anisotropic etching step, and the characteristic deterioration of the internal confinement type semiconductor laser device is suppressed.

[0015]

Embodiments of the present invention will be described with reference to FIGS. FIG. 9 is a cross-sectional view showing the main part of the internal constriction type semiconductor laser device, and FIGS. 6 to 8 are cross-sectional views showing the manufacturing process of the internal confinement type semiconductor laser device.

The layers that form the internal confinement type semiconductor laser device shown in FIG. 9 and are lattice-matched to each other are deposited by the MOCVD method.

[0017] That is, 3 × a Si 10 ^{1 8} cm ^{- 3} n containing
Prepare GaAs substrate 1 type, and lattice-matched composition n-an In ₀ overlaid on the _{substrate. 5 (G a 0. 3} Al 0. 7)
_{. 0 5} P impurity Si to 5 × ¹ 0 1 ⁷ as cm ^{- 3} and a thickness of 1μm of the cladding layer 2 provided taupe, In thereon
_A double heterojunction consisting of 0.5 (G a _0.5 Al _0.5 ) P active layer 3 is deposited. The active layer 3 is an undoped layer and has a thickness of 0.08 μm. The double heterojunction portion, composition _{P-In 0 5 (G a} 0 3 Al 0 7..) P to a thickness 1.0μm in Zn and _{^{5 × 10 1 8 cm -.}} 3 p -type cladding containing Deposit layer 4. _{Further, p-In 0. 5 G} a 0. 5 overlapping the etching stop layer 13 having the composition of P and lattice matched. This etching stop layer 13 contains Zn 7 ×
Contains 10 ¹⁸ cm ⁻³ and has a thickness of 0.05 μm.

Further, a current blocking layer having a stripe-shaped current injection portion A (see FIG. 9) which overlaps with the etching stop layer 13 and lattice-matches is arranged. The current blocking layers are n-In 0.5 in order from the side closer to the GaAs substrate 1 _.
(G a _1-X Al _X ) _0.5 P, that is, In _0.5 (G a _0.3 Al
_{X 0.7} ) _0.5 P the first layer 14a and G a
_{1 -.. Z Al Z As} (0 ≦ Z ≦ 1) That nG a _{0 7} Al _{0 3} constituted by the second layer 14b consisting of As, striped portions of the first layer 14a and second layer 14b After the removal, the contact layer 6 described later is deposited and lattice-matched to the current injection portion B.
Make up.

The first layer 14a contains 1 × 10 6 of Si as an impurity.
Containing ¹⁸ cm ^-3 and having a thickness of 0.2 μm, the second layer 14
b contains Si as impurities of 2 × 10 ¹⁸ cm ⁻³ and has a thickness of 0.8 μm.

The internal confinement type semiconductor laser device according to the present invention is provided with the contact layer 6 which is superposed on the current injection portion A and the first layer 14a and the second layer 14b constituting the current blocking layer 5 and which is lattice-matched. Form.

In order to form the stripe-shaped current injection portion A in the first layer 14a and the second layer 14b constituting the current blocking layer 5, as shown in FIG. 7, the stripe-shaped etching mask 12 (see FIG. 6). ) Is placed on the second layer 14b. The etching mask is provided with a window 10 having a width W, and the portion immediately below is etched by the RIE method using a halogen gas to expose the first layer 14a. Next, the first layer 1
4a is etched using hot phosphoric acid to expose the p-type cladding layer 4. As a result, a groove 12 to be the current injection portion A is formed, and 1 × 10 ¹⁹ with a composition of p-GaAs is formed therein.
cm ⁻³ of Zn is doped to deposit 5.0 μm thick contact layer 6 and lattice matched.

Finally, as shown in FIG. 9, p
The type electrode 7 and the n-type electrode 8 are formed to complete the InGaAlP internal confinement type semiconductor laser device 9 (see FIG. 9).

The thickness of the first layer 14a and the second layer 14b constituting the current blocking layer 5 is usually 0.8 μm as described above.
m, the latter being 0.2 μm, but the thickness d of the second layer 14b
Can be 0.1 μm ≦ d ≦ 0.5 μm. I.e.
In the case of 0.1 μm, the thickness of the first layer 14a becomes thinner than 0.8 μm, so that both layers 14a and 14b can be patterned by anisotropic etching. At this time, both layers 1
Since the thickness of 4a and 14b is thin, the damage caused by anisotropic etching is small, and the damage can be suppressed by the adjacent etching stop layer 13, and the crystal quality is not impaired.

When the thickness of the second layer 14b is larger than that of the first layer 14a as described above, the two-step treatment of anisotropic etching and isotropic etching is applied as described above. As a result, it is possible to maintain the predetermined laser device characteristics without impairing the crystal quality.

[0025]

In the InGaAlP internal confinement type semiconductor laser device according to the present invention, the double heterojunction is provided with the etching stop layer and the current blocking layer for depositing and lattice-matching the first layer and the second layer having different thicknesses. The structure. Furthermore, in order to remove the first layer and the second layer in a stripe shape, the second layer having a large thickness can be processed by anisotropic etching, and the second layer having a small thickness can be processed by isotropic etching.

That is, the current injection portion B is processed by a method in which the thick second layer is processed by anisotropic etching which may cause damage and the thin first layer is processed by isotropic etching.
In addition to improving the controllability of the width of the groove to be formed, the deterioration of the crystal quality immediately below the groove due to anisotropic etching is suppressed. This makes it possible to obtain an InGaAlP internal confinement type semiconductor laser device having good life characteristics and having less variation in characteristics within the semiconductor wafer.

[Brief description of drawings]

FIG. 1 is a sectional view showing a manufacturing process of a conventional InGaAlP internal confinement type semiconductor laser device.

FIG. 2 is a cross-sectional view showing the manufacturing process of the conventional InGaAlP internal confinement type semiconductor laser device following FIG.

FIG. 3 is a cross-sectional view showing the manufacturing process of the conventional InGaAlP internal confinement type semiconductor laser device following FIG. 2;

FIG. 4 is a cross-sectional view showing the manufacturing process of the conventional InGaAlP internal confinement type semiconductor laser device following FIG. 3;

FIG. 5 is a sectional view showing an outline of a conventional InGaAlP internal confinement type semiconductor laser device.

FIG. 6 is a cross-sectional view showing the manufacturing process of the InGaAlP internal confinement type semiconductor laser device of the present invention.

7 is a cross-sectional view showing the manufacturing process of the InGaAlP internal confinement type semiconductor laser device following FIG. 6;

8 is a cross-sectional view showing the manufacturing process of the InGaAlP internal confinement type semiconductor laser device following FIG.

FIG. 9 is a sectional view schematically showing an InGaAlP internal confinement type semiconductor laser device of the present invention.

[Explanation of symbols]

 1: Substrate, 2, 4: Clad layer, 3: Active layer, 5: Current blocking layer, 6: Contact layer, 7, 8: Electrode, 11: Etching mask 12: Groove, 13: Etching stop layer, 14a, 14b : First layer and second layer of current blocking layer, A: current injection part, B: damaged region.

Claims (2)

[Claims] 1. A GaAs substrate, an In _0.5 (G a _{1 -W} Al _W ) _0.5 P active layer and an In _0.5 (G a _{1 -Y} Al _Y ) layered and lattice-matched to the GaAs substrate _{. ) 0. 5 P (1 ≧} y> w ≧ 0)
The double heterojunction consisting of the cladding layer and the In _0.5 (Ga
_{1 -.} And _{U Al U) 0 5 P (} 0 ≧ u> 0.3) constituting the etching stop layer, a current blocking layer having a stripe-shaped current injection part of Cascade and lattice-matched to the etching stop layer, the A contact injection layer that overlaps the current blocking layer and the current blocking layer and is lattice-matched _.
a _1-X Al _X ) _0.5 P first layer and G a
_1-Z Al _Z As (0 ≤ Z ≤ 1) and a second layer, wherein the current injection part is formed by forming a stripe shape of the first layer and a part of the second layer. Type semiconductor laser device 2. A method of manufacturing an internal constriction type semiconductor laser device, characterized in that a part of the second layer is removed by a dry etching method, and a part of the first layer is removed by a chemical containing phosphoric acid.