JPH0414276A - Surface-emitting semiconductor laser element - Google Patents

Abstract

PURPOSE:To reduce the diameter of the active area and threshold current of the title laser element by forming a high-resistance area in a part where the current of an active layer is narrowed by irradiating the part with protons. CONSTITUTION:The first reflecting mirror 2 of a multilayered film composed of 25 pairs of n-Al0.1Ga0.9As and AlAs layers formed by alternately piling up the layers, the first n-Al0.4Ga0.6As clad layer 3, and p-Al0.15Ga0.85As active layer 4 are successively formed on an n-GaAs semiconductor substrate 1. After the entire surface of this wafer is coated with an SiO2 film 3, the SiO2 film is removed by etching except the central part where the film 13 is left in a circular form. A high-resistance area 12 is formed in a part of the active layer 4 by irradiating the surface of the part with protons by using the SiO2 film 13 as a mask. In order to suppress the diffusion of the electric current at the p-n junction, the area 12 is formed to the top of the first clad layer 2. After the entire surface is again coated with another SiO2 film, the film is removed only from a circular part above a current constricting section and an AuZn/Au light emitting window is formed by using the remaining SiO2 film as a mask. Finally, the SiO2 mask is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser device, particularly a surface emitting semiconductor laser device.

[Conventional technology]

Surface-emitting semiconductor laser devices emit laser light in a direction perpendicular to the substrate surface, and compared to normal semiconductor laser devices, they are capable of single-joint mode operation, large emission area, narrow emission angle, and two-dimensional array formation. It has been developed in recent years because it has many advantages such as:

This element has a structure in which a resonator is formed perpendicular to the substrate, and the light is resonated in the thickness direction of the stacked semiconductor films, and the laser light is emitted in the plane direction. A low threshold value can be obtained by increasing the reflectance of the reflecting mirror.

Conventionally, liquid phase epitaxy has been used to fabricate devices, but by using metal organic chemical vapor deposition (MOCVD), which has excellent flatness, film thickness controllability, and mass production, it is now possible to fabricate semiconductor films with different compositions. It is easy to form semiconductor multilayer mirrors that are alternately combined, and it is possible to have a structure in which the laser resonator is embedded in the crystal.

FIG. 5 is a schematic cross-sectional view showing an example of the structure of a surface-emitting semiconductor laser device manufactured using the MOCVD method. Fifth
In the figure, the second semiconductor laser element has a first semiconductor multilayer film reflection mirror 2 on the side of the pad j13 in which compound semiconductor films are laminated on the substrate l, and a second semiconductor multilayer film reflection mirror on the second cladding layer 5 side. A mirror 7 is formed, and a current confinement layer 6 is provided within the second cladding layer 5. Furthermore, a light transmitting film 8, a ring-shaped cap layer 9, and a ring-shaped electrode 10 are formed on the second semiconductor multilayer film reflecting mirror 7. 11 is a lower electrode. With such a structure, laser light is emitted from the center in a direction perpendicular to the thickness direction of the element.

[Problem to be solved by the invention]

In order to make the surface emitting semiconductor laser device as shown in FIG. 5 have a low threshold value, it is necessary to reduce the spread of the area of the active region. When the active region is circular, for example, the resonator length L-7μ7, the thickness d of the active layer 4 is 3n, and the reflection *R of the semiconductor multilayer film reflector 2.7 is 0.95. The relationship between the threshold current at a temperature of 300 K and the diameter of the active region is as shown in the diagram shown in FIG. active layer 4
In the structure shown in FIG. 5 in which current confinement is performed within the second cladding layer 5, it is not easy to reduce the diameter of the active region. Furthermore, adopting a structure in which regions other than the center of the active layer 4 are buried with a high-resistance layer or a pn reverse junction layer complicates the manufacturing process of the device, considering the thickness of the active layer 4, and reduces yield. It turns out.

The present invention has been made in view of the above points, and its purpose is to create a surface emitting semiconductor laser device with a small active region diameter and a low threshold current without using complicated means such as a buried structure. It is about providing.

[Means to solve the problem]

In order to solve the above problems, the surface emitting semiconductor laser device of the present invention is provided with a current confinement mechanism by irradiating protons to the part of the active layer where the current is constricted to form a high resistance region. .

[Effect]

The surface-emitting semiconductor laser device of the present invention, in which a high-resistance region is formed by irradiating protons to the current-confining portion of the active layer as described above, has a current confining effect equivalent to that of a buried structure, and reduces the A threshold current can be achieved.

〔Example] Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a schematic cross-sectional view showing the structure of a surface-emitting semiconductor laser device of the present invention, and parts common to those in FIG. 5 are designated by the same reference numerals. The difference between FIG. 1 and FIG. 5 is that a high resistance region 12 is formed in the active layer 4 by irradiating protons. Incidentally, a structure in which the current confinement layer 6 is provided is illustrated in FIG.

Next, a method for manufacturing the surface emitting semiconductor laser device of the present invention shown in FIG. 1 will be described. FIGS. 2(a) to 2(C) are schematic cross-sectional views showing the main manufacturing steps when this element is constructed from a G5As/Aj G5As-based material.

First, the n-G5As semiconductor substrate l (thickness loom,
carrier density I x 1010l8a') on n - A
I. , +Ga,, 25 pairs of wAs and ~As are alternately laminated (each layer thickness is λ/4). First multilayer film reflection @ 2 ,
n No, 4Ga6,6As (thickness Ig,
carrier density I x 10+s cffl-'')
') Land layer 3 and p Al a, +5Gao
, gsAs (thickness 3−, carrier density I × 10
I? C1l-') active layer 4 is sequentially formed [second
Figure (a)]. Next, the entire surface of this wafer is covered with a SiO□ film 1.
After coating with No. 3, a circular portion of 10 nΦ is left in the center, and the other areas are etched away. And 1on
Using the Sing film 13 of Φ as a mask, the wafer surface is irradiated with protons to form a high resistance region 12 in a part of the active layer 4. At this time, in order to suppress the spread of current in the pn junction, the high resistance region 12 extends to the top of the first cladding layer 3 [FIG. 2 Φ].

Next, after removing the SiO□ film 13 by etching, P JVo
, 4Gao, hAs (thickness 1-, carrier density I
10111cs-3) second cladding layer 5, p
-Ai @, lG30.9AS and A1As alternately 2
A second multilayer film reflecting mirror 7 with 5 pairs laminated (each layer pressure is λ/4)
+ P +'V++, zG3o, o-s (thickness 0.3n carrier density lXl0'' low 3) light transmitting film 8
．． p-GaAs (thickness 0.5ts, carrier density I
X 1019cs-3) cap layers 9 are sequentially laminated,
Furthermore, an electrode 10 of AuZn/Au is formed on the entire surface [FIG. 2 (C1)].

After that, after depositing a SiO
AuZn/Au electrode 1 using the remaining SiO□ film as a mask
0 and p-GaAs cap layer 9 are removed to form a light exit window, and finally the SiO□ mask is removed.

After that, an AuGe/Au electrode 11 is formed on the substrate 1 side,
By performing heat treatment for 110 minutes at 450° C. in an ox/N8 mixed gas atmosphere, a surface emitting semiconductor laser device having the structure shown in FIG. 1 can be obtained.

FIG. 3 shows a current-light output characteristic diagram at room temperature of the surface-emitting semiconductor laser device of the present invention fabricated as described above. From FIG. 3, the threshold current is about 10-A, and the It can be seen that current confinement is effectively achieved by irradiating a portion with protons to form a high resistance region.

In addition, in the device configuration shown in FIG. 1, the substrate l and the semiconductor multilayer film reflection #! 2, thickness 0.5n, carrier density lX
An n-GaAs buffer layer of 10" row 3 may be provided, and after proton irradiation is performed on a part of the active layer 4, a current confinement layer 6 is buried, as shown in FIG. 4 and similar to that in FIG. In this case, the current confinement is reliably performed together with the effect of the current confinement layer 6.

Although GaAs/JV GaAs-based materials have been described above, it is of course possible to select other material systems.

〔Effect of the invention〕

Surface-emitting semiconductor laser devices that have a resonator in a direction perpendicular to the substrate surface have a current confinement structure to lower the threshold current by reducing the diameter of the active region or by embedding a high-resistance layer. Conventionally, such means could not be easily carried out, but in the present invention, a part of the active layer is irradiated with protons to form a high resistance open castle, so it is possible to achieve sufficient current confinement equivalent to that of a buried structure. A surface-emitting semiconductor laser device with a low threshold current can be realized by a simple process.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of the surface-emitting semiconductor laser device of the present invention, and FIGS. 2(a) to (C) are schematic cross-sectional views showing the main manufacturing steps of the surface-emitting semiconductor laser device of the present invention. Third
The figure is a current-optical output characteristic diagram at room temperature of the surface-emitting semiconductor laser device of the present invention, FIG. 4 is a schematic cross-sectional view showing the structure of the surface-emitting semiconductor laser device of the present invention with a current confinement layer added, and FIG. 6 is a schematic cross-sectional view showing the structure of a conventional surface-emitting semiconductor laser device, and FIG. 6 is a diagram showing the relationship between the threshold current and the diameter of the active region of the surface-emitting semiconductor laser device. 1: Substrate, 2: First semiconductor multilayer film reflector, 3: First cladding layer, 4: Active layer, 5: Second cladding layer, 6: Current confinement layer, 7: Second semiconductor multilayer film reflector , 8: Light transmission film, 9: Cap layer, 10.11: Figure 1, Figure 3, Figure 2, Figure 4

Claims (1)

[Scope of Claims] 1) A surface-emitting semiconductor laser device comprising a first semiconductor multilayer reflector, a first cladding layer, an active layer, a second cladding layer, and a second semiconductor multilayer reflector on a semiconductor substrate. A surface-emitting semiconductor laser device, comprising a high-resistance region formed by proton irradiation in a portion of the active layer that constricts current. 2) A first semiconductor multilayer film reflector, a first cladding layer, an active layer, a second cladding layer, and a second semiconductor multilayer film reflector are provided on a semiconductor substrate, and current confinement is provided in a part of the second cladding layer. 1. A surface emitting semiconductor laser device having a layer, the surface emitting semiconductor laser device comprising a high resistance region formed by proton irradiation in a portion of the active layer that constricts current.