JPS62281390A - Semiconductor laser device and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable the high output operation to be performed by a method wherein a window structure to be N type at high concentration near the end of a resonator of an active layer and P type at high concentration in the other regions is formed by solid-diffusion of P type impurity diffused from a P type photoconductive layer as a diffusion source. CONSTITUTION:Zn is diffused to a P type Al0.25Ga0.75As photoconductive layer 5 passing through a contact layer 7 and an N type Al0.50Ga0.50As clad layer 6 from a part of SiO2 film removed by diffusion using closed pipe systwn such as vacuum sealing diffusion etc. In such a diffusion process, Zn is solid-diffused from the P type Al0.25Ga0.75As photoconductive layer 5 in high concentration through a P type Al0.50 Ga0.50As clad layer 4 in low concentration finally reaching an N type Al0.15Ga0.85As active layer 3 to reverse the conductivity type of active layer to P type. Then, N electrode 11 and P electrode 12 are formed respectively on the substrate side of wafer and the surface side. Through these procedures, a photoconductive layer with high refractive index can be formed through the intermediary of thin clad layers so that a semiconductor laser device capable of high output operation may be manufactured by solid-diffusion of P type impurity diffused from the P type photoconductive layer as a diffusion source.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a structure of a semiconductor laser capable of high output operation and a method of manufacturing the same.

[Conventional technology]

Conventionally, as a method to increase the output power of semiconductor lasers,
A so-called window structure is known in which the effective band gap near the end face of the resonator from which laser light is emitted is made larger than in the internal region.

For example, FIG.
Tam Elect 0=X (IEE[i JOURNAL
OF Qll-ANTt1MεLECTI? 0NICS
) VOL QE15 (1979) 775-78
This is an example of a window structure laser using Zn diffusion shown on page 1. In the figure, 1 is an n-type GaAs substrate, 13 is an n-type A
! ! o, 3 Gao, 7 As cladding layer, 14
is n-type Al1po6G aa, ypA s active layer, 1
5 is n-type A 'Q3 G a4? A s cladding layer, 1
6 is a 5j02 insulating film, I9 is a Zn diffusion region, 11 is an n electrode, and 12 is a p@ pole.

The manufacturing method and operation of this conventional laser will be explained. First, on the n-GaAs substrate 1, n-Al1ty3G
ao, 7 A s cladding 13, n A 1yo
6G az2As active layer 14, n A Rc) 3 G
ao, 7A 5 Each layer of the cladding layer 15 is crystal grown. After the growth, a 5io2 insulating film 16 is formed, and the 5i02 film 16 is removed in stripes leaving the vicinity of the cavity end face.

Zn is selectively diffused into the active layer 4 from the striped portions of the Si○2 film 16. As a result, the active layer 14 is n-type near the resonator end face, but is p-type inside and has a different conductivity type from the end face. According to this structure, the band gap energy of the p-type region in the active layer 14 becomes smaller than that in the undoped case due to the band tilling effect. On the other hand, the effective band gap energy of the n-type region in the active layer 14 becomes larger than that in the undoped case due to the Burstein effect. As a result, the n-type active layer region near the cavity facet becomes transparent to the laser light generated in the p-type active layer region, and absorption by the interface states at the cavity facet causes laser damage. is reduced, enabling high output operation.

[Problem that the invention seeks to solve]

However, according to this structure, it is necessary to accurately stop the Zn diffusion front 9 diffused from the surface of the contact layer through the n-AlβGaGaAs cladding layer 15 having a thickness of about 2 μm in the active layer region. If the ZnK powder does not reach the active layer, the window effect cannot be obtained. Also, Zn
When the diffusion reaches a region deeper than the active layer, the p-n junction shifts from the interface of the duffle heterostructure, resulting in a so-called remote junction, which causes problems such as an increase in threshold current and difficulty in oscillation itself. Therefore, as mentioned above, Zn
It is necessary to strictly control diffusion, and it is difficult to obtain good laser characteristics with good reproducibility and high yield.

Furthermore, in this structure, light confinement in the direction parallel to the active layer is achieved by a small refractive index difference due to the difference in the n-type and p-type conductivity types of the active layer, so that sufficient transverse mode control cannot be achieved. Also p-type.

Even a slight change in carrier concentration of each n-type causes a large change in the refractive index difference. As a result, there is a problem that the reproducibility and uniformity of device characteristics such as a threshold current and a far-field pattern of a radiation pattern deteriorate.

This invention was made in order to solve the above-mentioned problems, and its purpose is to provide a semiconductor laser device that has a window structure by p-type impurity diffusion, is capable of high output operation, and can be easily mass-produced with high yield. It is said that

[Means for solving problems]

In the semiconductor laser device according to the present description, an optical waveguide layer having a stripe-like p-type impurity concentration higher than that of the cladding layer and a refractive index higher than that of the cladding layer is formed through a thin cladding layer over the active layer except near the cavity end face. At the same time, solid-phase diffusion of p-type impurities using this p-type optical waveguide layer as a diffusion source results in a high concentration of n-type in the vicinity of the cavity end face of the active layer and a high concentration of p-type in the other regions. By forming a window structure, a semiconductor laser capable of high-output operation is realized.

[Effect]

In the semiconductor laser device according to the present invention, since the p-type impurity is diffused from the optical waveguide layer near the active layer, the diffusion distance is shorter than in the past, and the active layer region close to the optical waveguide layer is Since the refractive index is effectively larger than that of the active layer region away from the optical waveguide layer, a large refractive index difference also occurs in the direction parallel to the active layer, and as a result, transverse mode control becomes easily possible.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a semiconductor laser device according to an embodiment of the present invention, in which 1 is an n-type GaAs substrate, 2 ii″n
The type A la, soG aysoA s cladding layer 3 is, for example, an n-type A with a carrier concentration of about 3×10”cffl.
j2θ/lQ at2y6A s active layer, 4 is low concentration,
For example, a p-type A 1 asoG atuoAS cladding layer with a carrier concentration of I x 1017 cIn-3 or less, 5
is a p-type AlβGa4cosGa07yAs optical waveguide layer with a high concentration, e.g.
6 is an n-type A (laI6Gao, 30A s cladding layer), 7 is a p-type or n-type GaAs contact layer, 8 is a diffusion region formed by solid phase diffusion of Zn from the optical waveguide layer 5, and 9 is a closed tube type or an open type. Zn diffusion area by tube type, 10 is 5i
02 or a diffusion mask such as Si3N4, 11 is an n electrode, 1
2 indicates a p-electrode, respectively.

Hereinafter, a method for manufacturing a semiconductor laser device according to the present invention will be explained step by step with reference to FIGS. 2 to 5.

First, as shown in FIG. 2, an n-type GaAs substrate 1 is coated with an n-type A flasoGaasoAs cladding layer 2, an n-type Alc<BG aq/jA3 active layer 3, and a low concentration, for example, a carrier concentration I x 10'. ■゛33 or less type A 4
4. B) Gao,, g□As cladding 4, high concentration,
For example, 5 X 10'g ~ I X 101qcm-3
The above p-type, A tla, 2s G a6. )gA s
The optical waveguide layer 5 is successively crystal-grown by a liquid phase growth method, MOCVD method, or the like. Then, using photolithography technology, the resist film is left only on the striped portion, and the resist on the portion forming the window structure near the end face of the cavity is removed.

Next, only the optical waveguide layer 5 is formed of p-type A~5. .

Selective etching is performed to the surface of the Ga4B, As cladding layer, and the portions other than those covered by the resist film are removed.

FIG. 3 is a perspective view of this state, and FIG. 4 is a cross-sectional view taken along a plane perpendicular to the substrate in the longitudinal direction of the optical waveguide layer.

An example of an etching solution exhibiting such selectivity is an NH4OH/H202 solution. After etching and removing the resist film, an n-type GaAs cladding layer 6 and a p-type GaAs contact layer 7 are grown as a second growth. FIG. 5 shows a side view at this time.

After crystal growth, 5i02, SiN was used as a Zn diffusion mask.
An insulating film such as No. 4 is formed by vapor deposition, swabbing, or the like. Then, using a predetermined photolithography technique, the insulating film is removed only from the portions mentioned above or above the edges. Next, Zn is applied to the contact layer 7 and the n-type A 1pnG from the part where the SiC2 film is removed by diffusion using a closed tube method such as vacuum confinement diffusion.
aρ, p-type A 1a2 through HAs cladding W16
(G a47zA s diffuses until it reaches the optical waveguide layer 5. In this diffusion step, Zn is transferred from the high concentration p-type A I!a6G ap7sA s light guide '6Ji55 to the low concentration p-type A flpgoG aDsoA s cladding layer. solid phase diffusion through 4, and finally n-type A phantom/S G
The aaB As reaches the active layer 3, inverts the conductivity type of the active layer and changes to p-type. N electrode 11 on the substrate side of the wafer
, the device is completed by forming a p-electrode 12 on the front surface side.

This structure further suppresses the current spread and lowers the threshold current by using low concentration p-type A 1/6oG aσrOAs.
The thinner the cladding layer 4 is, the better. Also, from the viewpoint of diffusion controllability, it is better to make this layer thinner, for example, 0.5 μm.
It is desirable to set it to less than m.

Next, the highly concentrated waste p-type A %alG ap, 75A s optical waveguide layer 5 has the function of transverse mode control in the direction parallel to the resonator, and its function will be explained. FIG. 6 shows a cross-sectional view at the edge in the direction perpendicular to the resonator end face and a schematic diagram of the effective refractive index distribution in the horizontal direction.

The region of the active layer that is close to the optical guide layer is affected by the refractive index of the optical guide layer located above it, which is larger than that of the cladding layer, and the optical waveguide layer is formed on the active layer. The effective refractive index difference between the area and the area without the area becomes large. Therefore, a step-like refractive index distribution occurs in the direction parallel to the active layer,
Light is effectively confined in the lateral direction, thereby making it possible to reduce the threshold current.

In addition, in the above example, Aj! Although GaAs semiconductor lasers have been described, other mixed crystal systems such as InGaAsP,
Al. It goes without saying that similar effects can be obtained with a Ga1nP semiconductor laser.

(Effects of the Invention) As described above, according to the present invention, a striped optical waveguide layer having a refractive index higher than that of the cladding layer is formed on the active layer excluding the vicinity of the cavity end face via a thin cladding layer. , due to the solid-phase diffusion of p-type impurities using this n-type optical waveguide layer as a diffusion source, a high concentration of n
By forming a window structure in which the other regions are n-type with a high degree of 1 degree, it is possible to improve the controllability of p-type impurity diffusion and control the transverse mode, resulting in excellent device characteristics and high output that is suitable for mass production. This has the effect of providing an operable semiconductor laser device.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view including the optical waveguide layer in the cavity direction of a semiconductor laser according to an embodiment of the present invention, FIG. 2 is a perspective view of the above embodiment after the first crystal growth, and FIG. FIG. 4 is a cross-sectional view including the optical waveguide layer in the direction of the chisel, and FIG. 5 is a cross-sectional view including the edge portion in the direction of the resonator after the second crystal growth. FIG. 6 is a cross-sectional view including the optical waveguide layer of the cleaved end face of the semiconductor laser of the above embodiment, and a diagram showing the effective refractive index distribution in the active layer. FIG. 7 is a perspective view of the conventional semiconductor laser device and the cavity end face. 1 is a partial cross-sectional view showing a Zn diffusion region in a direction perpendicular to .1-=n-type GaAs substrate, 2-.n-type A (!q5v
G at2E. As cladding layer, 3-n type A AθBG ayzHA
s active layer and 4.--low concentration p-type A 14g. Qa/
rQA S cladding layer, 5...high concentration n-type A decay G
ag5A s optical waveguide layer, 6 ・-n type A 7! p5oG
ajgoA s cladding layer,? - P-type GaAs contact layer, 8... Diffusion region from optical waveguide layer, 9... Zn diffusion region by closed tube or open tube method, 10...
Insulating film, 11...n electrode, 12...p electrode, 13-
n-type A (la3 Ga47A s cladding layer, 14
-n-type A et ty6 Ga, q (, AS activity, 9.1
5- n-type A 11O3G aa7A s cladding layer,
16-sio2 insulation film. Figure 1 6nIzuAlo, 5oGao, 5oAsri7. , JJ1
2: ptGo Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Procedural amendment (spontaneous) August-0, 1988 1, Indication of case Patent application No. 124571-1988 2
Title of the invention: Semiconductor laser device and manufacturing method 3; Person making the amendment 5; Claims column of the specification to be amended; Detailed description of the invention column 6; Contents of the amendment (1) Description of the specification The scope of claims is amended as shown in the attached sheet. (2) "19" on page 5, line 13 of the specification is corrected to "9". (3) Delete "selectively" from the second to third lines of page 6. Claims (1) An n-type semiconductor substrate, an n-type first cladding layer formed on the semiconductor substrate, and an n-type active layer having a smaller forbidden band width and a higher refractive index than the first cladding layer. , a p-type second cladding layer having a larger forbidden band width and a lower refractive index than the active layer; a second cladding layer having a refractive index formed on the second cladding layer in a stripe shape except for the vicinity of the resonator end face; a p-type optical waveguide layer that is larger than the active layer and smaller than the active layer;
a cladding layer, an n- or p-type contact layer for electrocutting mounting, and a p-type impurity diffusion region forming a striped current confinement structure reaching from the p-type contact layer to the optical waveguide layer; Except for the area near the cavity end face of the above active layer of the main hill, a window structure consisting of a highly doped p-type region inverted by solid-phase diffusion of p-type impurities in region-2- and a highly doped n-type region near the end face is formed. (2) A GaAs substrate as the semiconductor substrate, klz Ga1-X AS as the first cladding layer, Al.Ga, -yAs as the active layer, and the second cladding layer. A e s Ga +-11A!, Al trowel Gaz-aLAs is used as the optical waveguide, A Rp Gai-pAs is used as the third cladding layer, and the AJ
2. The semiconductor laser device according to claim 1, wherein the composition ratios of Ga and Ga are such that x, y, z, α, β satisfy the following relationship: 0≦y and α<x, z, β. (3) The semiconductor laser device according to claim 1, wherein either zinc (Zn) or magnesium (Mg) is used as the p-type impurity. (4) An n-type semiconductor substrate, an n-type first cladding layer, an n-type active layer, a p-type second cladding layer, and a stripe formed on the second cladding layer except for the vicinity of the resonator end face. A p-type optical waveguide layer, an n-type third cladding layer formed on the second cladding layer and the optical waveguide layer, an n- or p-type contact layer for attaching an electrode, and 38 p-type contact layer to optical waveguide layer. A p-type impurity diffusion region S2 forms a striped current confinement structure reaching the area, and further solid-phase diffusion of p-type impurity from a region of the optical waveguide layer excluding the vicinity of the resonator end face of the active layer. A method for manufacturing a semiconductor laser device having a window structure consisting of a highly doped p-type region inverted by a p-type region and a highly doped n-type region near an end face, the method comprising: a striped current confinement structure formed by the p-type impurity diffusion region; When forming the p-type impurity, a silicon oxide film or a silicon nitride film is used as a diffusion mask for the p-type impurity, striped openings are formed only in the vicinity of the optical waveguide layer, and the p-type impurity is diffused by thermal diffusion using the closed-tube method or the open-tube method. While reaching the optical waveguide layer through the contact layer and the third cladding layer, the second cladding layer and the active layer immediately below the optical waveguide layer are inverted to p-type by solid phase diffusion from the optical waveguide layer. A method for manufacturing a featured semiconductor device. (5) The optical waveguide layer is A ji! cc G at-zA
(0<α≦0.25), and the third cladding layer consists of AJ/JGa/−As (β≧0.35).
) When forming the striped optical waveguide layer, a mixed solution of ammonia water (N Ha ○H) and hydrogen peroxide water (H2O2) is used, in which the etching rate sharply decreases when the AgH composition ratio of the material to be etched is 0.25 or more. 5. The method of manufacturing a semiconductor laser device according to claim 4, wherein a selective etching solution is used.

Claims (5)

[Claims] (1) an n-type semiconductor substrate, an n-type first cladding layer formed on the semiconductor substrate, an n-type active layer having a smaller forbidden band width and a higher refractive index than the first cladding layer, and a n-type active layer having a higher refractive index than the first cladding layer; a p-type second cladding layer with a large band width and a small refractive index; a p-type second cladding layer having a larger refractive index than the second cladding layer and an active layer formed on the second cladding layer in a stripe shape except for the vicinity of the cavity end face; a p-type optical waveguide layer smaller than the active layer;
A cladding layer, an n- or p-type contact layer for attaching an electrode, and a p-type impurity diffusion region forming a striped current confinement structure reaching from the p-type contact layer to the optical waveguide layer, The active layer has a window structure consisting of a highly doped p-type region inverted by solid-phase diffusion of p-type impurities from the region excluding the vicinity of the cavity end face, and a highly doped n-type region near the end face. Features of the semiconductor laser device. (2) The semiconductor substrate is a GaAs substrate, the first cladding layer is Al_xGa_1_-_xAs, the active layer is Al_yGa_1_-_yAs, the second cladding layer is Al_zGa_1_-_zAs, the optical waveguide layer is Al_αGa_1_-_αAs, the third
A patent claim characterized in that Al_βGa_1_−_βAs is used as the cladding layer, and the relationship of the composition ratios of Al and Ga to x, y, z, α, and β is 0≦y<α<x, z, β. The semiconductor laser device according to item 1. (3) The semiconductor laser device according to claim 1, wherein either zinc (Zn) or magnesium (Mg) is used as the p-type impurity. (4) An n-type semiconductor substrate, an n-type first cladding layer, an n-type active layer, a p-type second cladding layer, and a stripe formed on the second cladding layer except for the vicinity of the resonator end face. A p-type optical waveguide layer, an n-type third cladding layer formed on the second cladding layer and the optical waveguide layer, an n- or p-type contact layer for electrode attachment, and an optical waveguide layer from the p-type contact layer. It has a p-type impurity diffusion region that forms a striped current confinement structure reaching the
The optical waveguide layer further includes a highly doped p-type region inverted by solid-phase diffusion of p-type impurities from a region of the active layer excluding the vicinity of the cavity end face, and a highly doped n-type region near the end face. A method of manufacturing a semiconductor laser device having a window structure, which comprises using a silicon oxide film or a silicon nitride film as a p-type impurity diffusion mask to form a stripe-like current confinement structure using the p-type impurity diffusion region, and forming a light guide. Striped openings are formed only in the vicinity of the wave layer, and the p-type impurity is caused to reach the optical waveguide layer via the contact layer and the third cladding layer by thermal diffusion using a closed tube method or an open tube method, and at the same time, the optical waveguide is A method for manufacturing a semiconductor device, comprising inverting a second cladding layer and an active layer immediately below an optical waveguide layer and an active layer to p-type by solid-phase diffusion from the layer. (5) The optical waveguide layer is made of Al_αGa_1_−_αAs (0<α≦0.25), and the third cladding layer is made of Al_αGa_1_−_αAs (0<α≦0.25).
Consists of l_βGa_1_−_βAs (β≧0.35)
When forming the striped optical waveguide layer, ammonia water (NH_4OH) and hydrogen peroxide water (NH_4OH) and hydrogen peroxide water (NH_4OH) and hydrogen peroxide water (NH_4OH), whose etching rate decreases rapidly when the Al composition ratio of the material to be etched is 0.25 or more, are used.
5. The method of manufacturing a semiconductor laser device according to claim 4, wherein a selective etching solution consisting of a mixed solution of H_2O_2) is used.