JPS5810874B2 - Hand Thai Hatsukousoshi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor light emitting device having an extremely narrow current concentration region width.

Conventionally, a semiconductor laser device is a typical example of a light emitting device that concentrates current in a narrow area on a straight line.

The conventional type of such a semiconductor laser is shown in Figure 1a.
It becomes like ~e.

FIG. 1A shows what is called an electrode stripe or 5i02 stripe, in which 11 is an electrode provided with a narrow width, and current concentration is attempted to be achieved by narrowing the width of the electrode 11.

Figure 1 shows a so-called planar stripe structure, in which the electrical conductivity type of the final layer 12a is made different from that of the layer directly below it, and the final layer 12a is formed by a diffusion method or the like only on a narrow necessary portion 12b.
The electrical conduction type is different from 2a, and unnecessary parts are p- during operation.
The n-junction is placed in a reverse bias state, and current is concentrated in the necessary portion 12b.

In reality, the width through which the current flows in the vicinity of the junction is larger than the width of the electrode 11 in FIG. It is also difficult to limit the thickness to 10 μm or less.

What has been done to improve these problems is shown in FIGS. 1C to 1E.

That is, Fig. 1C shows a proton bombardment stripe in which the unnecessary part 13 is made to have high resistance against current concentration by ion implantation, and Fig. 1D shows a mesa stripe in which the unnecessary part 14 is chemically removed. FIG. 1e shows what is called a junction stripe in which the electrical conduction type is changed by diffusing into the unnecessary portion 15.

In the cases shown in FIGS. 1c to 1e above, in order to obtain the desired width of the current limiting region, an ion implantation method, a method of chemically removing unnecessary portions, and a method of changing the electrical conductivity type are used.

In this case, the narrower limit of the width of the current concentration region is determined by the mask width such as the thickness of the metal line during ion implantation, or the width of the resist line in the case of photolithography, and is usually 5 μm. It is extremely difficult to make the width narrower than the width.

This invention was developed in view of the above-mentioned points. Grooves are created by chemical polishing, etc. using a mask having a width obtained by conventional photolithography, and the cross-section of the grooves is created by appropriately selecting the plane orientation of the crystal. The groove is made into an inverted trapezoid shape so that the width at the bottom is narrower than the width at the groove surface, and this bottom is brought close to the bonding surface that contributes to light emission. A low resistance layer is uniformly formed by a diffusion method, etc., and a current is applied to the bottom of the groove. By utilizing the concentration, it is possible to obtain a current concentration region width that is significantly narrower than a conventional current concentration region width.

The present invention will be explained below with reference to the drawings.

FIG. 2 shows an example in which the present invention is applied to a normal GaAS-GaAlAS heterojunction laser.
1 is a p-GaAS thin layer as an optically active layer, 22 is a p-GaAlAS layer for confining carrier and light to the PGaAs thin layer 21, and 23 is for low resistance contact to the electrode. It is a p-GaA three layer.

Such a multilayer crystal is obtained by sliding liquid phase growth using n-GaA3 as a substrate.

A groove 24 having a width W is provided on the surface of this crystal.

In this case, if (001) is used for the crystal surface, the crystal plane index [11
1] and (111) can be obtained.

In the figure, θ is about 54°, which makes it possible to make the bottom width W2 narrower than the groove width W1 on the crystal surface.

After that, the chemical polishing mask is removed, and a p-type impurity such as Zn (zinc) is added to the entire surface by thermal diffusion or ion implantation, thereby forming a low resistance layer 25 shown with diagonal lines in the figure. .

Thereafter, electrodes 26 and 27 are provided, and the semiconductor light emitting device is assembled on a suitable heat sink or the like.

In the operating state, the current is concentrated in a region 28 of the optically active layer, that is, a part of the p-GaA3 thin layer 21, which corresponds to the low resistance width W at the bottom of the groove 24.

According to the experimental results, W1=5 μm. When W2≈0, W could be reduced to about 1 μm by Zn diffusion for 1 hour.

By concentrating the current in such a narrow region, the threshold current of the semiconductor laser can be significantly reduced, making it possible to achieve an operating current value of several tens of mA, which is about the same as that of a display light emitting diode.

Unlike the conventional method shown in Figures 1a and d, there is no need to place an electrode directly above the current concentration area where the current density is high and is most susceptible to deterioration. Deterioration is reduced because the partial sides are not exposed.

Furthermore, since the gain in the p-GaAs thin layer 21 changes uniformly and smoothly, and the loss is also constant, it also has the characteristic that the oscillation posture of the laser beam tends to be uniform.

In the embodiment shown in FIG. 2, the three p-GaA layers 23 (all 23) are used as the n-GaAs layer as the top layer crystal, and the depth of the low resistance layer 25 in which Zn is diffused is set to this n-GaAs layer.
It is clear that if the layer is made shallower than the three GaA layers, the current concentration effect becomes even stronger, since the characteristics shown in FIG. 1 can be added.

However, the above embodiments are based on n-GaAlAS, p-GaAS,
This was about a semiconductor laser consisting of four layers of p-GaAIAS and p(n)-GaA, but in addition to this, n-G
aAS, p-GaAS.

The present invention can be similarly applied to a single heterojunction semiconductor laser such as p-GaAlAS.

Furthermore, if the structure is such that light is extracted perpendicularly to the bonding surface by excluding the electrodes in the portions corresponding to the grooves, it can also be applied to light-emitting display elements that display symbols or characters depending on the shape and arrangement of the grooves.

As semiconductor light emitting device materials, GaAs as mentioned above,
In other words, it is not limited to GaAIAS-based light emitting devices, but also GaP-based,
Of course, other crystals such as InP-based crystals may also be used.

As explained in detail above, the present invention provides a method for etching a semiconductor light emitting device made of a multilayer crystal by etching it from the surface of the crystal using an etchant selective to the plane orientation of the crystal, so that at least one layer having a width at the bottom surface is narrower than the width at the surface of the crystal is etched. A groove is formed, and an impurity is doped from the crystal surface including this groove to form a low resistance layer, and the bottom part of the groove is made into a current concentration area, so that the width of the groove at the crystal surface is Even if the accuracy of photolithography is kept above a certain level, the width of the bottom surface can be made narrower than the width of the crystal surface by etching with an etchant that is selective to the plane orientation of the crystal. It has excellent features such as being able to make the concentrated portion much narrower than in the past, thus lowering the threshold current and reducing deterioration.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A to 1E are schematic cross-sectional views showing conventional semiconductor lasers each having a current concentration effect, and FIG. 2 is a cross-sectional view showing an embodiment of the present invention. In the figure, 21 is a pGaAs thin layer, 22 is a p-GaAlAS
23 is a p-GaAs layer, 24 is a groove, and 25 is a low resistance layer.

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor light emitting device made of a multilayer crystal, including the step of etching from the crystal surface with an etchant that is selective to the plane orientation of the crystal to form at least one groove whose width at the bottom surface is narrower than the width at the crystal surface. . A method for manufacturing a semiconductor light emitting device, comprising the step of adding impurities from the crystal surface including the groove to obtain a low resistance layer, the bottom part of the groove being a current concentration area.