JPS62166581A - Semiconductor laser device and manufacture thereof - Google Patents

Abstract

PURPOSE:To completely remove an adverse influence of a barrier layer of an MQW layer on an injecting current without limiting the degree of freedoms of designing an active layer by forming a P-N junction boundary perpendicularly to the inward direction of a multiplex quantum well layer and parallel to a laser light outputting direction, and further forming P- and N-electrodes parallel to the P-N junction boundary. CONSTITUTION:A P-N junction boundary is formed perpendicularly to the inward direction of a multiplex quantum well layer and parallel to a laser light outputting direction, and P- and N-electrodes are formed parallel to the P-N junction boundary. Thus, a current injected from the electrodes flows completely parallel to the surface of the well layer, and injected to the P-N junction boundary without influence of a barrier layer. A substrate is etched perpendicularly to provide vertical sidewalls 26, 27 for forming the P-N junction boundary and the electrodes. A mask for impurity diffusion or ion implantation is formed by emitting an oblique beam and depositing a thin film.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a semiconductor laser device and a manufacturing method thereof that are widely used in industries such as optical communication, optical measurement, and optical calculation. This has a great effect on the characteristics of the device.

2. Description of the Related Art Currently, semiconductor laser devices used as light sources or optical functional elements in fields such as optical communication, optical measurement, and optical calculation are actively being developed in various fields, and some of them are at the stage of practical application. . In such a situation.

Lower threshold and temperature stabilization of semiconductor laser devices.

It is expected to have effects such as improved monochromaticity, low loss as a light guide, and selectivity of the plane of polarization. A multiple quantum well layer was provided in the active layer. The so-called ivf Q W (Mu 1 t i
A half-four body laser device (abbreviation for Quan tum W'el l) has been proposed and development is progressing.

Figure 3 shows a schematic diagram of a typical MQW semiconductor laser device (
The energy band diagram of the active layer (MQW layer (MQW layer) (0)) of the same figure is shown as an example.

Tsang, et al., Appl, Phys.
Lett, 39(10).

15, November, 1981, p. 7
86)].

In FIG. 3(a), an active layer (MQW layer) 1 is formed on a semiconductor substrate 2 with a cladding layer 3 interposed therebetween, on which one cladding layer 4 is formed, and electrodes 5.6 are formed above and below. is provided. Still, in the same figure (b), an energy band diagram of an active layer (MQW layer) 1 composed of four quantum wells 9 surrounded by a barrier layer 7 and a cladding layer 8 is shown, and the lateral direction shows the active layer. The direction is perpendicular to the layer plane, and the valence band 10, the forbidden band 11. A conduction band 12 is shown in each case.

Generally, in an MQW semiconductor laser device, by carefully adjusting the depth of the quantum wells 9 and the thickness of the barrier layer 7, the coupling between the quantum wells 9 is weakened, and as a result, an ideal transition spectrum between quantum levels can be obtained. In such a structure, as shown in Figure 3, when the current injection direction is perpendicular to the active layer surface, the active layer (MQW layer) The carriers injected into quantum well 9 cross a high barrier and are injected into quantum well 9, resulting in an increase in device resistance and a decrease in injection efficiency.

Reflecting the above facts, an MQW semiconductor laser device has a structure in which the current injection direction is parallel to the active layer surface, for example, a so-called T 7 S (Transverse Jun
It has been proposed to introduce a 5tripe) structure.

FIG. 4 shows an example of a schematic diagram of a semiconductor laser device having a TTS structure [for example, [Heterostraft Lasers J (H, C, Ca5ey, et al.).

Heterogstructure La5ers, p
artB, 1978゜p, 230. Academy
c Press, New York)]
. In this case, the current injected through the electrode 5 passes through the PN junction interface 13 and reaches the electrode 6.

14 is an insulating layer, and 15 is a current blocking layer. Light emission occurs near the region where the active layer (MQW layer) 1 and the PN junction interface 13 intersect. Therefore, in a semiconductor laser device having such a structure, phenomena such as an increase in element resistance and a decrease in injection efficiency due to the barrier layer 7 are more likely to occur than in a semiconductor laser device having a structure shown in FIG. 3(a). can be improved.

Problems to be Solved by the Invention As mentioned above, in the semiconductor laser device having the structure shown in FIG. 3(a), the degree of freedom in designing the MQW structure of the active layer is reduced, and Since the characteristics cannot be maximized, it has been proposed to introduce the structure shown in Figure 4, but even in this case, the current injection direction is not completely parallel to the active layer surface. Further, due to the irregularity of the current path, problems remain from the viewpoint of efficient current injection into the light emitting region. Furthermore, the manufacturing and device structure are complicated due to the introduction of insulating layers, current blocking layers, etc.

Means for Solving the Problems In order to solve the above-mentioned problems, in the present invention, PN
Taking measures such as forming the bonding interface perpendicular to the in-plane direction of the multi-quantum well layer and parallel to the laser beam extraction direction, and further forming both the P electrode and the N electrode parallel to the PN bonding interface; In order to provide an effective and efficient manufacturing method for a semiconductor laser device, impurities are introduced from one sidewall of the vertical etching by performing ion beam etching and oblique beam thin film deposition in the same device. Measures were taken to provide a bonding interface and to provide the P and N electrodes by depositing metal thin films on both sides of the sidewalls.

Function By forming the PN junction interface perpendicular to the in-plane direction of the multi-quantum well layer and parallel to the laser beam extraction direction, and further forming both the P electrode and the N electrode parallel to the PN junction interface, the The current flows completely parallel to the plane of the multiple quantum well layer and is injected into the PN junction interface without being influenced by the barrier layer. Therefore, there is no restriction on the degree of freedom in designing the MQW structure of the active layer, and the reduction in reactive current still contributes to uniform light emission in the light emitting region.

Furthermore, in principle, there is no need for an insulating layer, a current blocking layer, etc. for current direction control.

After forming a multiple quantum well layer on a semiconductor substrate, the substrate on which the multiple quantum well layer is formed is vertically etched using an ion beam etching method having anisotropic etching characteristics, thereby forming the PN junction. It is possible to provide vertical sidewalls forming the interface as well as the electrodes. However, it is possible to form a mask for impurity diffusion or ion implantation without going through a phosphorography process by irradiating an oblique beam with one of the vertical sidewalls in the shadow and depositing a thin film. Furthermore, since the above-mentioned etching and thin film deposition are both performed using a beam, they can be processed in the same device (named ion beam processing device), which in turn simplifies the manufacturing process. Contributes to cleaning the interface of the deposited thin film.

Embodiment FIG. 1 shows a schematic diagram of an embodiment of the semiconductor laser device of the present invention. In the figure, an active layer (MQW layer) 19 is formed on a semi-insulating substrate 16 and sandwiched between undoped epitaxial layers 17 and 18.
The barrier layer in the active layer (MQW layer) 19 is doped with N-type impurities, and the resulting quanta are accumulated in the quantum level of the quantum well layer, so that as a result, the quantum well layer in the active layer (MQW layer) 19 becomes N-type. This structure prevents recombination of carriers in the quantum well layer from occurring via the impurity level, and still prevents carrier recombination in the quantum well layer from reaching the impurity level when traveling in the quantum well. It is possible to prevent the scattering caused by

Furthermore, by setting the energy gap of the epitaxial layers 17 and 18 to be larger than that of the barrier layer in the active layer (MQW layer) 19, the injected current is efficiently parallel to the multi-quantum well layer in the quantum well. It starts to flow.

The shaded area is a P-type impurity diffusion layer 2o, in which a PN junction interface 21 is formed perpendicular to the active layer (MQW layer) 19 surface and parallel to the laser beam extraction direction 22, and a P electrode 23 and an N electrode 24 are formed. , are both formed parallel to the PN junction interface 21.

Next, an embodiment of the manufacturing method of the present invention will be described based on FIG. First, an undoped epitaxial layer 17° active layer (MQW layer) is formed on a semi-insulating semiconductor substrate 17.
19. The undoped epitaxial layer 18 is epitaxially grown in sequence (FIG. 4(a)). Next, a stripe mask 25 having an arbitrary width parallel to the laser beam extraction direction is provided, and using the mask 26, each of the layers 17, 18, 1
9 is vertically etched using a reactive ion beam etching method to obtain vertical side walls 26 and 27 (
Figure (b)). By using a vertical reactive ion beam etching method, damage-free vertical etching with good surface stoichiometry of the layers 17, 18, and 19, which are usually binary or more mixed crystal semiconductors, can be expected.

The same equipment used in the process shown in Figure (b) (with the plasma generation chamber and etching (or deposition) chamber separated).
Thin film deposition is performed in an apparatus (commonly referred to as an ion beam processing apparatus) by tilting the substrate 16 so that the vertical sidewall 26 shadows the incident beam 28 for thin film deposition. That is, a thin film 29 is formed on the surface except for the vertical sidewalls 26 (FIG. 3(C)).

Then, using the thin film 29 as a mask, a P-type impurity element is diffused to form a PN junction interface 21 ((d) in the same figure).
)). Finally, using the thin film 29 as a mask, the P electrode 23 is
((e) in the same figure), the thin film 29 is peeled off, and a new thin film 30 is formed in the same manner as the previous thin film, and using this as a mask, the N electrode 24 is formed ((e) in the same figure). (
f)).

By the manufacturing method described above, a semiconductor laser device as shown in FIG. 1 is realized. However, the manufacturing method described above is basically a phosphorography process.

It is a simple product that does not require as much as wet method 1, and furthermore, it can be handled entirely by a beam application process in a vacuum, making it possible to conduct the entire manufacturing process in a vacuum without exposing it to the atmosphere. In particular, it has the advantage that various interfaces within the semiconductor laser device can be cleaned.

On the other hand, the present invention provides a photonic integrated circuit due to the fact that both the P and N electrodes are formed on the substrate, and that when forming the vertical sidewalls, it is also possible to form the end faces of the 7-application-Perot resonator at the same time. It is also suitable for responding to

As described in detail, the present invention has an active layer (MQW layer).
(in other words, allows a design that maximizes the characteristics of the MQW structure), and
Provided is an MQW semiconductor laser device having a structure that can completely eliminate the adverse effects of a barrier layer on injection current (for example, an increase in device resistance, a decrease in injection current, etc.), and yet still improves the simplicity of the semiconductor laser device. This brings about great concrete effects, such as providing a manufacturing method that can provide various interfaces that are clean and clean.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a semiconductor laser device according to an embodiment of the present invention;
FIG. 2 is a process diagram showing an embodiment of the manufacturing method of the present invention, and FIGS. 3 and 4 are schematic diagrams showing a conventional semiconductor laser device. 1.19... Active layer (MQW layer), 7...
・Barrier layer, 9...Quantum well, 13.21...
...PN junction interface, 14...Insulating layer, 15.
... Current blocking layer, 20 ... P-type impurity diffusion layer, 22 ... Laser light extraction direction, 23 ...
...P electrode, 24...N electrode, 26.27.
...Vertical side wall. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure? ? Z/ Figure 2 2 (3) Figure 3

Claims (2)

[Claims] (1) The active layer consists of a multiple quantum well layer, so-called MQ
W configuration, characterized in that the PN junction interface is formed perpendicular to the in-plane direction of the multi-quantum well layer and parallel to the laser beam extraction direction, and the P electrode and N electrode interfaces are both formed parallel to the PN junction interface. Semiconductor laser device. (2) After forming a multiple quantum well layer on a semiconductor substrate, the multiple quantum well layer is vertically etched by ion beam etching using a stripe mask having an arbitrary width parallel to the laser beam extraction direction. In the same equipment used for the etching, a thin film is deposited by irradiating an oblique beam so that one of the vertically etched sidewalls is in the shadow, and using this as a mask, PN is deposited by impurity diffusion or ion implantation. A semiconductor laser device comprising the steps of forming a bonding interface perpendicular to the in-plane direction of the multiple quantum well layer and in the laser light extraction direction, and forming a P electrode and an N electrode on each of the vertically etched side walls. manufacturing method.