JPH0680861B2 - Method for manufacturing semiconductor light emitting device - Google Patents

Description

DETAILED DESCRIPTION [Outline] An indium phosphorus crystal layer or a III-V group mixed crystal layer containing indium and phosphorus as a main component on an active layer of a III-V group mixed crystal containing indium provided on a substrate. In the manufacture of a buried semiconductor light emitting device having a structure, after forming a band-shaped reverse mesa shape including an active layer, a mixed solution of hydrogen bromide, hydrogen peroxide and water is used as an etching solution to remove the side surface of the reverse mesa shape. By shaping, the crystal plane orientation of the side surface of the active layer is prevented from being (111) A.

[Industrial application field]

The present invention is directed to a III-V containing indium provided on a substrate.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an embedded semiconductor light emitting device having an indium phosphorus crystal layer or a group III-V mixed crystal layer containing indium and phosphorus as a main component on an active layer of a group mixed crystal. Concern

Semiconductor light emitting devices similar to the above include, for example, BH (Buried H
There is a laser.

A laser such as a BH laser is used as an optical signal source for optical communication because of its relatively small oscillation threshold current, and further reduction of the oscillation threshold current is desired.

[Conventional technology]

 FIG. 2 is a schematic side sectional view of a conventional BH laser example.

In the figure, 1 is an n-type indium phosphide (InP) substrate,
Reference numeral 2 is an n-type InP buffer layer, 3 is an active layer of indium gallium arsenide phosphide (InGaAsP) which becomes a light emitting region, and 4 is p-type InP.
Of the clad layer 5, the clad layer 4, the active layer 3, and the buffer layer 2 form a strip-shaped (the direction perpendicular to the drawing is the longitudinal direction) inverted mesa shape light emitting portion, and 6 is a p-type InP current blocking layer. ,
7 is an n-type InP current blocking layer, 8 is silicon dioxide (Si
An insulating layer of O ₂ ), 9 and 10 are metal electrodes.

In this laser, when a current is passed from the electrode 9 to the electrode 10, the current is concentrated in the light emitting section 5 due to the existence of the PN junction in the opposite direction formed by the current blocking layers 6 and 7. When the current is increased to a certain value (oscillation threshold current) or more, laser oscillation occurs and laser light is emitted from the active layer 3.

The manufacturing procedure of this laser is shown in FIG.
~ (C).

That is, as shown in FIG. 3A, the buffer layer 2, the active layer 3, and the cladding layer 4 are deposited on the entire surface of the substrate 1 by, for example, a liquid phase growth method.

Then [see FIG. 2B], Si is formed on the upper surface of the light emitting portion 5 forming region.
After the O ₂ mask 11 is formed, the light emitting portion 5 is formed by etching using bromine methanol as an etching solution until the active layer 3 is exposed on the side surface.

Next (see FIG. 7C), the current blocking layers 6 and 7 are deposited by, for example, a liquid phase growth method while leaving the mask 11 as it is.

Next, referring to FIG. 2, after removing the mask 11, the insulating layer 8 and the electrodes 9 and 10 are formed and cleaved to complete.

[Problems to be solved by the invention]

In the BH laser manufactured as described above, the crystal plane orientation of the side surface of the light emitting portion 5 is (111) A.

The indium (I
Since n) is generated, an oxide film is formed on the side surface of the light emitting portion 5, and a defect occurs at the interface with the current blocking layers 6 and 7.

For this reason, when the above-mentioned current is passed, a part of the current concentrated in the light emitting portion 5 flows through the interface and does not contribute to light emission, and there is a problem that the oscillation threshold current becomes large.

In order to solve this problem, it is known that the side surface of the light emitting portion 5, especially the side surface of the active layer 3 should not be the (111) A plane.

As a measure for this, it has been proposed to use a mixed solution of hydrogen bromide (HBr), hydrogen peroxide (H ₂ O ₂ ) and water (H ₂ O) as an etching solution for forming the light emitting portion.

However, in this method, the light emitting portion is as shown in FIG. 5a, and the width W2 of the upper surface of the light emitting portion 5a becomes too narrower than the width W1 of the active layer 3 to form the width W1 to a desired width, for example, about 1.5 μm. There is a problem that is difficult to do.

[Means for Solving Problems] The above problem is that an active layer to be a light emitting region of a III-V mixed crystal containing In is formed on a semiconductor substrate and an InP crystal layer or I layer is formed on the active layer.
After depositing a III-V group mixed crystal layer containing n and phosphorus (P) as main components and etching from the crystal layer or the mixed crystal layer side to form a band-shaped inverted mesa shape including the active layer , HBr and H ₂ O ₂ and H
This is solved by the manufacturing method of the present invention in which a mixed solution with ₂ O is used as an etching solution to shape the side surface of the inverted mesa shape.

[Action]

A mixed solution of HBr, H ₂ O ₂ and H ₂ is an etching solution which does not form a (111) A surface as an etched surface for InP crystals or III-V group mixed crystals containing In and P as a main component. Is.

Therefore, even if the side surface of the inverted mesa shape is formed on the (111) A surface, the side surface of the light emitting portion becomes a surface other than the (111) A surface by adding the etching with the mixed solution to form the light emitting portion. Also, since the etching is performed in the reverse mesa shape, the above-mentioned problem that the width W2 becomes too narrower than the width W1 does not occur.

Thus, for example, it becomes possible to manufacture a BH laser having an active layer having a desired width and having a reduced threshold current.

〔Example〕

Hereinafter, an embodiment of the method of the present invention will be described with reference to FIGS. The same reference numerals denote the same objects throughout the drawings.

The object of this embodiment is a BH laser corresponding to that shown in FIG.

That is, [see FIG. 7A], n is formed on the entire surface of the n-type InP substrate 1.
Type InP buffer layer 2 (thickness about 2 μm), InGaAsP active layer 3 (thickness about 0.2 μm), p-type InP clad layer 4 (thickness about 1 μm), p-type InGaAsP cap layer 12 (thickness) About 0.2μ
m) is deposited by, for example, a liquid phase growth method.

Next, as shown in FIG. 3B, as in the case of the conventional example shown in FIG. 3, a mask 11 is formed and then etching is performed using bromine methanol to form a light emitting portion 5 in which the active layer 3 is exposed on the side surface. In the conventional example, the light emitting section 5 is completed, but the side surface is the (111) A plane, so the following etching is added in this embodiment.

Then, referring to FIG. (C), the mask 11 is left as it is and HB
Mixture of r, H ₂ O ₂ and H ₂ O (47 wt% HBr 4cc, 31 wt%
H ₂ O ₂ of ₂ cc and H ₂ O of 20 cc) are used to slightly etch the constricted portion under the light emitting portion 5 (for example, at room temperature for about 1 minute). To form.
The side surface of the light emitting portion 5b becomes almost vertical with the (111) A plane disappearing.
In this embodiment, the light emitting section 5a is completed.

Then, as shown in FIG. 6D, the current blocking layers 6 and 7 are deposited by, for example, a liquid phase epitaxy method while leaving the mask 11 as in the case of the conventional example. Despite both sides of the mask 11 projecting to the outside of the light emitting portion 5a, the current blocking layers 6 and 7 sufficiently fill both outsides of the light emitting portion 5a.

Then, [see FIG. 2], as in the case of the conventional example, a mask
After removing 11, the insulating layer 8 and the electrodes 9 and 10 are formed and cleaved to complete.

The inventor of the present application manufactured and compared BH lasers in which the dimensions of the active layer 3 were substantially equal by the method of the above-described embodiment and the method of the conventional example shown in FIG. As a result, the former threshold current is about 15
It was confirmed that the value was mA, which was reduced to about 1/2 of the latter value of about 30 mA.

In the above embodiment, the mask 11 is used as a mask for the etching shown in FIG. 1C, and the etching rate is set so that the side surface of the light emitting portion 5b is substantially vertical.
Although a larger cap layer 12 is provided, the gist of the present invention is
Since the (111) A plane does not appear on the side surface of the light emitting portion 5b and the width of the upper surface does not become too narrow, the side surface of the light emitting portion 5b does not have to be vertical, so there is no problem. It may not be necessary, and another mask having a width different from that of the mask 11 may be used for the above etching.

Further, the material of the active layer 3 in the above embodiment is InGaAsP, but other materials such as aluminum gallium indium arsenide (AiGaInAs) may be used as long as it is a III-V mixed crystal containing In. Can be easily inferred to be effective.

〔The invention's effect〕

As described above, according to the configuration of the present invention, an indium phosphide crystal layer or indium and phosphorus as main components is provided on a III-V group mixed crystal active layer containing indium provided on a substrate.
In manufacturing a buried type semiconductor light emitting device having a III-V group mixed crystal layer, it is possible to make the active layer have a desired width and prevent the crystal plane orientation of its side surface from being (111) A.
For example, it has an effect of enabling the manufacture in which the threshold current of the BH laser is reduced.

[Brief description of drawings]

FIG. 1 is a sectional view (a) of a process sequence of an embodiment of the method of the present invention.
(D), FIG. 2 is a schematic side sectional view of an example of a conventional BH laser, and FIG. 3 is a sectional side view in the order of steps of laser production shown in FIG. 2 (a).
(C), FIG. 4 is an explanatory view of the improved and proposed manufacturing method. In the figure, 1 is a substrate, 2 is a buffer layer, 3 is an active layer, 4 is a cladding layer, 5 is a light emitting part, 5a and 5b is a current blocking layer, 8 is an insulating layer, 9 and 10 are electrodes, 11 is a mask and 12 is a cap layer.

Claims (1)

[Claims] 1. III-V containing indium on a semiconductor substrate
An active layer which becomes a light-emitting region of a group mixed crystal and on which an indium phosphide crystal layer or indium and phosphorus as the main components III-
A group V mixed crystal layer is deposited and etched from the crystal layer or the mixed crystal layer side to form a band-shaped inverted mesa shape including the active layer, and then hydrogen bromide, hydrogen peroxide and water are mixed. A method of manufacturing a semiconductor light emitting device, characterized in that a liquid is used as an etching liquid to shape the side surface of the inverted mesa shape.