JPH0434987A - Semiconductor laser and manufacture thereof - Google Patents

Abstract

PURPOSE:To facilitate an injection of a current, to make it possible to make low an oscillation threshold current value and to manufacture a semiconductor laser, which is suitable as a parallel integrated light source for optical information processing use, by a method wherein a laser main body part, which is provided with a first conductivity type clad layer, an active layer and a second conductivity type clad layer, an electrode part and an electrode mounting pattern part are provided on an semi- insulating semiconductor substrate and the pattern part is provided with a vacancy for isolating the second conductivity type clad layer from the first semiconductivity type clad layer by the side of the active layer. CONSTITUTION:A second conductivity type clad layer 13 on an active layer 12 is pushed out in the horizontal direction and an electrode mounting pattern part 15 having a pore 14 is provided by the side of the layer 12, whereby problems, such as the difficulty of the formation of electrodes, an increase in a contact resistance to the electrodes and the like, can be improved. Moreover, as the sectional area of a current path can effectively be made large, the resistance of the parts of the clad layers can also be reduced. Moreover, as a current is made to flow in parallel to a film, the problem of the discontinuity of a heteroband can also be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor laser used for optical transmission and optical information processing.

(Prior art) Semiconductor lasers are key light sources for optical communication and optical information processing.In particular, recently, surface-emitting semiconductor lasers that oscillate in a direction perpendicular to semiconductor substrates have been used for data transmission between computers and optical computing. It is being actively researched as an indispensable key device. This is because light can transfer data through space without wires, so it is expected that semiconductor lasers will have a high spatial parallel processing ability when integrated in parallel in addition to single elements.

(Problems to be Solved by the Invention) For semiconductor lasers suitable for such parallel integration, formation of electrode patterns of conventional elements has been a problem. For example, as a conventional surface emitting semiconductor laser, Electronics Letters
As described in Vol. 25 (1989), pp. 1377-1378 of ``S), current was supplied to the device only by a test wire. This surface-emitting semiconductor laser has a cylindrical vertical cavity structure.
In the resonator, the active layer is sandwiched between upper and lower semiconductor multilayer films that serve as reflecting mirrors, and current passes vertically through the semiconductor multilayer films and is injected into the active layer. In this case, a conventional problem has been that it is difficult for current to flow due to band discontinuity at the hetero interface of the semiconductor multilayer film.

SUMMARY OF THE INVENTION An object of the present invention is to provide a parallel-integrable semiconductor laser that overcomes the above-mentioned conventional difficulties in electrode pattern formation.

(Means for Solving the Problems) A semiconductor laser of the present invention includes a laser main body portion including a cladding layer of a first conductivity type, an active layer, and a cladding layer of a second conductivity type, and an electrode portion on a semi-insulating semiconductor substrate. , the electrode mounting has a pattern portion, and the electrode mounting has a hole beside the active layer in the pattern portion for isolating the cladding layer of the second conductivity type from the cladding layer of the first conductivity type. do.

The method for manufacturing a semiconductor laser of the present invention includes the steps of sequentially growing a first conductivity type cladding layer, an active layer, and a second conductivity type cladding layer on a semi-insulating semiconductor substrate, and forming a laser main body portion, an electrode portion, and the like. To attach the electrode with a narrow width, a mask pattern having a pattern portion is provided on the second conductivity type cladding layer, and the cross-sectional shape is etched by at least one of the oblique incident ion beam etching method and the chemical etching method that reflects the crystal orientation. is etched into an inverted mesa shape, and the electrode mounting includes a step of providing a hole beside the active layer to isolate the second conductivity type cladding layer from the first conductivity type cladding layer in the pattern portion.

(Function) As the resonator size of the semiconductor laser is made smaller, the size of the electrode forming part also becomes smaller, making it easier to form the electrode pattern.
And the contact resistance of the electrode also increases. Further, in the case of a surface emitting semiconductor laser that uses a semiconductor multilayer film as a reflective film, charge depletion and accumulation due to Peter band discontinuity inhibit the conductivity of current in the direction perpendicular to the film. On the other hand, FIG. 1 is a perspective view of an embodiment of the present invention.As shown in FIG. By providing a pattern section 15 for electrode mounting, problems such as difficulty in forming the electrode and increased contact resistance with the electrode can be alleviated. 7 Furthermore, since the cross-sectional area of the current path can be effectively increased, the resistance of the cladding layer portion can also be reduced. Can be reduced. Furthermore, by allowing current to flow parallel to the membrane, the problem of Peter band discontinuity can be avoided.

In order to protrude the cladding layer over the active layer and provide a pattern for attaching the electrodes, a complicated process such as embedding and regrowth can be considered, but in the present invention, a simple process as shown in Fig. 2 is used.
Electrode attachment with holes 14 beside the active layer formed a pattern 15. Figure 2 shows a schematic manufacturing process diagram.
After the film has grown as shown in Figure 2(a), a narrow mask pattern 21 is provided in the electrode mounting area as shown in Figure 2(b), and oblique incident ion beam etching is performed as shown in Figure 2(e). . The effect of the obliquely incident ion beam 23 is to make the etching cross-sectional shape into an inverted mesa shape, and instead of obliquely incident ion beam etching, chemical etching that reflects the crystal orientation may be used.

(Example) FIG. 2 (aXbXc) is a schematic cross-sectional view of an element explaining a first example according to claims 1 and 2 of the present invention. On a semi-insulating GaAs substrate 10, an n-type semiconductor multilayer film made of AlAs/GaAs and an n-type A film each having a thickness equivalent to 1/4 wavelength are formed.
N-type cladding layer 11 made of lxGa1-xAs, active layer 12 made of non-doped InGaAs, P-type AlxG
a1-xAs and AlAs with a thickness equivalent to 174 wavelengths/
P-type cladding layer 1 made of GaAs P-type semiconductor multilayer film
3 was grown by molecular beam epitaxy (MBE). After further laminating the electrode film 20 (FIG. 2(a)), a narrow resist mask pattern 21 and a laser main body mask pattern 22 are formed at the electrode mounting portion (FIG. 2(b)).
, reactive ion beam etching (R) using chlorine gas
By using the IBE method and tilting the incident angle of the ion beam onto the sample from the perpendicular to the sample substrate, an electrode attachment pattern 15 was formed with an inverted mesa-like cross section and a hole 14 at the core of the active layer. FIG. 2(c) is a sectional view of the electrode attachment at the pattern portion. This structure makes it possible to inject current in the horizontal direction, reducing leakage current caused by high voltage when injecting current in the vertical direction of conventional semiconductor multilayer films, and resulting in a smaller threshold current value than in the past. Ta. Furthermore, in this structure, the resistance at the electrode and cladding layer 13 was less than half that of the conventional structure. In addition, it became easy to increase the reflectance of the multilayer film by increasing the number of semiconductor multilayer films, and a significant reduction in the oscillation threshold current value was also obtained in this respect. In this example, the active layer width of the laser main body is 211 m x 2 pm, and the electrode pattern 16 is 3 pm.
Rectangle x311m, electrode mounting pattern part 15 is lpm
Width. A first conductivity type electrode pattern 17 was formed on the extracted first conductivity type cladding layer 11 .

In this embodiment, one electrode section 42 is provided in one laser main body section, but two or more electrode sections 42 may be provided. For example, if the electrode sections 42 are provided on the left and right sides of the laser main body, the resistance of the electrode sections and the cladding layer section can be reduced to 115 or less, and the threshold value of the layer can be lowered.
This makes it possible to achieve higher efficiency.

As a second embodiment, in the etching process according to claim 2 of the present invention, instead of the oblique incidence method of ion beam etching of embodiment 1, the pressure of the etching gas is increased to use chemical etching properties to form an inverted mesa shape. Electrode attachment formed pattern 15. At this time, the electrode attachment pattern direction was selected to be the <011> direction, which provides an inverted mesa cross section. With this method, the process was simple and optical damage was small, so extremely high-quality oscillation characteristics were obtained.

FIG. 3 shows an element of the first embodiment of the present invention on a semi-insulating substrate 10.
FIG. 3 is a schematic plan view of an element when the elements are stacked in parallel on top. Both the basic element and the basic process of the present invention are suitable for integration, and each element can be driven with a low threshold current value.

Although FIG. 1 shows a case where the active layer/clad layer cross section parallel to the plane is rectangular, the cross section may be circular, elliptical, or polygonal. Further, the active layer may have a single or multiple quantum well structure. Regarding the material system, InGaAs
Instead, use AlGaAs or AIGaInP in the visible light range.
/GaInP-based lasers and long-wavelength InGaAsP/InP-based lasers are also effective. Further, the first conductivity type and the second conductivity type of n and p may be exchanged. Although this embodiment has been described using a surface emitting type semiconductor laser as an example, the present invention is also applicable to a conventional horizontal resonator type semiconductor laser.

(Effect of the invention) .

The semiconductor laser of the present invention and its manufacturing method can facilitate current injection and lower the oscillation threshold current value compared to the conventional semiconductor laser, and are therefore suitable as a parallel integrated light source for optical information processing.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a device showing a semiconductor laser which is an embodiment of the present invention, FIG. 2 (aXbXc) is a schematic process diagram of a semiconductor laser manufacturing method of the present invention, and FIG. 3 is a parallel integration diagram of the present invention. FIG. 2 is a schematic element plan view of the element. In each figure, 10...Substrate, 11...First conductivity type cladding layer, 1
2... Active layer, 13... Second conductivity type cladding layer, 1
4...Vacancy, 15...Electrode mounting pattern part, 16,
17... Electrode pattern, 18... Light, 20... Electrode film, 21, 22... Mask pattern, 23... Obliquely incident ion beam, 31, 32... Current conduction pattern, 41... ... Laser body part, 42... Electrode part

Claims (2)

[Claims] (1) A laser body comprising a cladding layer of a first conductivity type, an active layer, a cladding layer of a second conductivity type, an electrode part, and an electrode attachment pattern part on a semi-insulating semiconductor substrate, and the electrode 1. A semiconductor laser having a hole beside an active layer for separating a cladding layer of a second conductivity type from a cladding layer of a first conductivity type in a mounting pattern portion. (2) a cladding layer of a first conductivity type on a semi-insulating semiconductor substrate;
A process of sequentially laminating and growing an active layer and a cladding layer of the second conductivity type, and forming a mask pattern having a laser main body portion, an electrode portion, and a narrow electrode attachment pattern portion connecting them to the second conductivity type cladding layer.
The electrode mounting pattern is formed on the conductive cladding layer and etched to have an inverted mesa cross-sectional shape by at least one of oblique incident ion beam etching or chemical etching that reflects the crystal orientation. A method for manufacturing a semiconductor laser, comprising the step of providing a hole beside an active layer to isolate a second conductivity type cladding layer from a first conductivity type cladding layer.