JPH03288477A - End face light emitting diode and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce leak currents and minimize a separation part by providing a separation part, which consists of an opposite conductivity of impurity diffusion layer, between a light emitting part and a light absorbing, for the upper clad layer, which was the leak current passage between the light emitting part and the light absorbing part, so as to elevate electric resistance. CONSTITUTION:The base composed of a substrate 51, a lower clad layer 59, an active layer 61 and an upper clad layer 63 is equipped with a light emitting part 65 in the stripe direction of a V groove 57, a separation part 67 for separating the light emitting part 65 and a light absorbing part 69, and said light absorbing part 69 for absorbing the light generated from one end of the light emitting part 65. The separation part 67 is one which is formed by diffusing p-type impurities, for example, Zn down to the depth not reaching the active layer 61 to the separation part formation planned part of the upper clad layer 63. Moreover, though basically the light absorbing layer 69 is of the same structure as the light emitting part 65, it is constituted by diffusing p-type diffusions from the surface of the upper clad layer 63 to the lower clad layer 59.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to an edge-emitting diode and a method for manufacturing the same.

(Prior Art) Edge-emitting diodes have advantages such as being able to obtain a practical level of optical coupling output even with single-mode optical fibers.

However, this type of diode has a light emitting part with a so-called stripe structure, and its structure is similar to that of a semiconductor laser. When the temperature was increased, stimulated emission could occur in the light emitting part. When stimulated emission occurs in this way, the edge-emitting diode that should output spontaneous emission light ends up outputting laser light, which poses a problem.

Therefore, various attempts have been made to suppress the occurrence of stimulated emission.

An example of an edge-emitting diode for which such an attempt has been made is, for example, the document related to the applicant of this application (Canon Allens on Lasers and Electrodes).
Ontics (CLE○: Conference o
n La5ersand Electro ○p
tics), Tme M39 (1988) p, 356~
1:nGaAsP, /InP disclosed in 357)
There was a type of edge-emitting diode. FIG. 4 is a schematic perspective view of this edge-emitting diode cut so that the light emitting part is vertically divided.8 This edge-emitting diode basically has a stripe structure that emits light by current injection. The light emitting section 11 has a light emitting section 11, and a light absorbing section 13 having a stripe structure is provided on the extension of the light emitting section 1 in the stripe direction to absorb light generated from one end of the light emitting section 11. Its detailed structure was as described below.

In this edge-emitting diode, an InP substrate 21 of the first conductivity type (in this case, the p-InP substrate 2), a current confinement layer 23 of the second conductivity type (nInP layer 23), and a current confinement layer 23 of the first conductivity type The constriction layer 25 (p-InP layer 25) was laminated in this order. Roughly, p-
A first groove 27 was formed in a stripe-like groove having a depth extending from the surface of the 1nP layer 25 to the p-InP substrate 2 and having a V-shaped cross section when cut in a direction perpendicular to the stripe direction. Furthermore, a second V-groove 29 was formed in a region of the substrate 21 eight spaces apart from the region where the first V-groove 27 was formed so as to be striped or coaxial with the first V-groove 27. Inside the first and second V-grooves 27 and 29 and on the substrate portion between these grooves, there are a p-InP lower cladding layer 31, a p-InGaAsP active layer 33, and an n-I
The nP upper claride layer 35 is laminated in this order to form a so-called 0
The day structure was tI4 omitted. However, in the region between the first and second V-grooves 27 and 29, the molecular side cladding layer, etc., which does not have a groove, is located at a higher position than the part inside the groove, so the active layer 33a in the first V-groove and the second The active layer 33b in the V-groove is the portion 23 of the InP layer 23.25 formed as a current confinement layer.
a, 25a.

Roughly speaking, in this edge-emitting type Gioto, 100-I n
An n-InGaAsP cap layer 37 is formed on the upper rat layer, and the first V groove 2 of this cap layer 37 is
nflll'IIM on the area opposite to 7.

A Si○2 film 39 is provided on the other area where the pole 38 is provided.
T-covered, roughly, under the p-InP substrate 21 and 1
1 was provided with a p-side electrode 41.

When this edge-emitting diode is driven, current is effectively injected into the first V-groove 27 because it is confined only in the portion 1 of the cap layer 37 exposed from the 5in2 film 39. As a result, the area force 1 light emitting portion 11 of the first V groove 27 is formed. Further, the active layer 33b in the second V groove 29 is
The same composition as the active layer 33a in the V-groove 27 (active layer 33b
may be made of a material whose band gap is shorter than the emission wavelength of 33a. ), but band filling (band fi111n9) occurs when driving the diode.
The effect allows it to absorb light.

Therefore, in this edge-emitting diode, out of the light emitted by the light emitting part 1, the light directed towards the light absorbing part 3 is transmitted to the light absorbing part 1.
3, the light reflection at the end face of the light absorbing portion 13 of the dionide was prevented, and the resonator mode due to stimulated emission was prevented.

(Problem to be Solved by the Invention) However, in the conventional edge-emitting diode described above, the light-emitting part and the light-absorbing part were connected through the n-InP upper claride layer, so when a current is passed through the light-emitting part, the current A part of the light also leaks to the light absorbing section 13, resulting in a problem that the absorption coefficient of the light absorbing section for the emission wavelength of the light emitting section becomes small.

Therefore, until the light reaches the end face on the light absorption part side of the edge-emitting diode (in order to obtain sufficient light attenuation, the length of the light absorption part in this diode must be 400 gm). The element size has become large.Roughly speaking, in order to reduce the leakage current from the light emitting part to the light absorption part, the area M between the light emitting part and the light absorption part (23a in FIG.
, 25a) had to be as long as 150 umf, and since the light emitting section was 150 um, the total length of the device reached 700 um.

In addition, in the conventional edge-emitting type Gioto described above, the active layers 33a, 331) of the light-emitting part and the light-absorbing part are in the M area t'
! t (I n P layers 23a, 25a), so of the light generated in the light emitting part, the light directed toward the light absorption part is separated from the light emitting part! It is reflected at the interface with the region and is fed back to the light emitting section.Therefore, when a high current is injected into the light emitting section, there is a risk that oscillation due to stimulated emission may occur.

This invention has been made in view of the above points, and therefore, the object of the invention is to provide a system that does not have discontinuities in the active layer and can sufficiently electrically separate the light-emitting part and the light-absorbing part. An object of the present invention is to provide an edge-emitting diode having a structure and a method for easily manufacturing the same.

(Means for Solving the Problem) In order to achieve this object, according to the first invention of this application, a substrate of a first conductivity type and a lower cladding of the first conductivity type formed on the substrate are provided. layer, an active layer and an upper cladding layer of a second conductivity type, a light emitting portion having a stripe structure,
In an edge-emitting diode that includes a light absorption part with a striped structure for absorbing light generated from one end of the light emitting part, τ is applied to the part between the light emitting part and the light absorption part of the base from the surface of this part to the upper side. The separation part is formed by diffusing impurities of the first conductivity type to a depth that reaches the active layer () and does not reach the active layer. It is characterized in that impurities of the first conductivity type are diffused to a depth that reaches the side crat layer.

Further, according to the second invention of this application, a substrate of a first conductivity type, a lower uralad layer of the first conductivity type, an active layer, and a lower cladding layer of the second conductivity type formed on the substrate. A light-emitting part with a striped structure,
This is an edge-emitting type diode comprising a light-absorbing part with a striped structure for absorbing light generated from one end of the light-emitting part. It is formed by diffusing impurities of the first conductivity type to a depth that reaches the upper cladding layer but does not reach the active layer. In manufacturing an edge-emitting type GIO, in which impurities of the 14th conductivity type are diffused in the active layer (reaching the 5mm depth or the depth e-M reaching the lower cladding layer), impurities of the 1st conductivity type are diffused. The method is characterized in that the diffusion is carried out according to the following procedure 0) or (2).

■The thickness of the part of the upper cladding layer corresponding to the light-absorbing part σ) should be made thinner than that of the part corresponding to the light-emitting part and the light-absorbing part. A first conductive pear impurity is introduced into the base.

(2) A thin film is formed on a portion of the upper Urarado layer corresponding to the area between the light emitting part and the light absorbing part, and then an impurity of the first conductivity type is introduced into the aforementioned base from above the upper cladding layer.

(Function) According to the configuration of the first invention, most of the region in the thickness direction of the upper cladding layer of the second conductivity type between the light emitting part and the light absorption part is formed from the impurity diffusion layer of the first conductivity type. Therefore, the separation resistance between the light-emitting part and the light-absorbing part of the upper Urarado layer becomes higher than in the case where there is no impurity diffusion layer.

Furthermore, in the light absorption section, each layer is of the same conductivity type (first conductivity type) due to the diffusion layer of the first conductivity type, so even if there is a leakage current, no light is emitted. Therefore, the absorption coefficient does not decrease due to light emission. Since impurities are diffused into the active layer of the light-absorbing portion, the absorption coefficient of the light-absorbing portion can be increased by the light-absorbing action of the impurities.

Further, according to the configuration of the second invention, the distance from the base surface to the active layer between the light emitting part and the light absorption part can be longer than the distance from the base surface to the active layer in the light absorption part. Therefore, even if the impurity of the first conductivity type is diffused in the region between the light emitting part and the light absorption part and the region of the light absorption part in the same process, the position N relationship between the tip of the diffusion layer and the active layer in the double head region will not change. It can be made different for both head areas. Therefore, the diffusion layers of the separation section and the light absorption section can be formed in the same process.

(Embodiments) Hereinafter, embodiments of the edge-emitting diode of the first invention and embodiments of the manufacturing method of the second invention will be described with reference to the drawings.

Note that each figure used in the following explanation schematically shows the dimensions, shapes, and M distribution relationships of each structure IIi command to the extent that these inventions can be understood.

First, an embodiment of the edge-emitting diode (hereinafter sometimes abbreviated as "diode") of the first invention will be described.

FIGS. 1(A) to (D) are diagrams for explaining the diode. FIG. 1(A) is a perspective view of this diode, and FIG. 1(8) is a perspective view of this diode. A cross-sectional view taken along line I, FIG.
A cross-sectional view taken along the U line, Figure 1 (D) is the first
FIG. 3 is a cross-sectional view taken along the mm line in FIG.

Note that in FIGS. 1C and 1D, hatchings indicating cross sections are omitted except for the impurity diffusion layer in order to avoid complicating the drawings.

The edge-emitting diode of this embodiment has a pInP substrate 5.
1, an n-InP current confinement layer 53 and a p-InP current confinement layer 55 are sequentially provided. Roughly speaking, the groove 57 is a striped groove having a depth from the surface of the o-InP current confinement layer 55 to the p-InP substrate 51 and a stripe width of about 2 um, and has a figure-9 cross section in the direction perpendicular to the stripe direction. Equipped with.

Further, on this V groove 57 is a p-InP lower crat layer 5.
9, p-InGaAsP active layer 6] and n-InP upper claride layer 63. The active layer 61 has a crescent-shaped cross section within the V-groove 57 perpendicular to the stripe direction.

Although omitted in this embodiment, an n-InGaAsP main cap layer may be provided on the low InP upper cladding layer 63.

Furthermore, in the edge-emitting diode of this embodiment, a light emitting portion 65 is formed along one stripe direction of the V-groove 57 on the base composed of the substrate 51, the lower cladding layer 59, the active layer 61, and the upper cladding layer 63. , a portion M section 67 for separating the light emitting section 65 and the light absorbing section 69 , and a light absorbing section 69 for absorbing light generated from one end of the light emitting section 65 .

The length I21 of the light emitting part 65, the length I22 of the M part 67, and the length g3 of the light absorption part 69 are not limited to these, but in this embodiment, β1 is 150 um, 1! 2”i
25 Ll m , 123'=300 um.

Further, a width side electrode 71 is provided on a region of the n-InP upper claride layer 63 corresponding to the light emitting portion 65, and a width side electrode 71 is provided on the p-InP substrate 51.
A p-side electrode 73 is provided on the back surface of each. When a voltage is applied between the p-side and n-side electrodes 71 and 73, the n-side electrode 7
A current is injected into the DH (double hetero) junction below 1 and light emission occurs.

The isolation section 67 is formed by diffusing a p-type impurity, such as Zn, into the region where the M section is to be formed, to a depth that does not reach the active layer 61 (FIG. 1(D) 9). (see).

The light absorbing section 69 basically has the same structure as the light emitting section 65, but differs in that the p-type impurity is diffused from the surface of the upper cladding layer 63 to the lower cladding layer 59. (See Figure 1(C)).

Note that the diffusion depth of the p-type impurity in the light absorption section 69 is as follows:
In this embodiment, the depth is set to reach the lower cladding layer, but if the active layer is p-type as in this embodiment, the purpose can be achieved even if the depth reaches the active layer.

Next, a so-called 1D button for making a lid will be described as an embodiment of the second invention using an example in which the manufacturing method of the second invention is applied to manufacturing the edge-emitting diode described with reference to FIG. Figure 2 (A) - (
C) is a manufacturing process diagram for explaining the process, and FIG.
It is a process diagram shown by the perspective view corresponding to.

First, an n-InP current confinement layer 53 and a p-InP current confinement layer 55 are sequentially grown on the p-InP plate 51 by, for example, a liquid phase growth method (FIG. 2(A)).

Next, using known film formation techniques, photolithography techniques, and etching techniques, 1) a mask (not shown) made of, for example, SiO2 is formed on the -InP current confinement layer 55, exposing the region where the V groove is to be formed; Thereafter, for example, the p-InP current confinement layer 55 is etched using a known wet etching technique 1.
and n-InP! The flow constriction layer 53 is etched to a depth that reaches the substrate 51 to form a striped V-groove 57 (FIG. 2(B)).

Next, on the structure in which the V groove 57 has been formed, a p-InP lower clamp layer 59, a p-InP lower crad layer 59, a p-InP
GaAsP active layer 6 ] and n-InP upper claride layer 6
3 to grow sequentially.

Next, a mask (not shown) is formed on the n-InP upper cladding layer 63 so that the portion corresponding to the light absorption portion 69 (see FIG. 1(A)) is filled out, and the other portion is covered. Thereafter, the portion of the upper cladding layer exposed through the mask is etched by a predetermined amount using, for example, a known wet etching technique. Here, the predetermined etching amount refers to the shape of the Zn diffusion layer for the M portion and the Zn diffusion layer for the light absorption portion, which will be etched later.
! i, in the same process, there is a local difference in the thickness of the upper cladding layer so that the tip of the former diffusion layer does not reach the active layer and the tip of the latter diffusion layer at least reaches the active layer. is the amount that can be added.

Next, remove this mask. Due to this etching, the thickness of the portion of the upper cladding layer 63 corresponding to the light absorption portion 69 becomes thinner than the other portion (FIG. 2(C)).

Next, on the upper cladding layer 63, a portion of the upper cladding layer 63 corresponding to a region where the separation portion 67 (see FIG. 1A) is to be formed and a portion corresponding to the light absorption 8B69 have a window exposed, for example, SiO2, Ax20. A mask made of a material selected from , SiN4, etc. is formed using a known technique.

Next, the wafer tZn3P or ZnP with this mask is
sealed in a quartz ampoule with a diffusion source of 2nd class, 6
Heat treatment is performed at a temperature of 00° C. for about 1 hour, and the Zr+7a wafer is diffused into the portion exposed from the mask. In this case, the thickness of the upper cladding layer 63 is thicker at the portion corresponding to the area where the 1st portion is to be formed or at the portion corresponding to the light absorption portion, so that the tip of the diffusion layer formed by the above-mentioned Zn diffusion treatment is located at the separation portion 67. In the light absorbing portion 69, the light does not reach the active layer 61 and reaches the lower crat layer 59. As a result, two desired types of diffusion layers can be formed in the same diffusion process (see Figures 01 (A), (C), and CD).

Next, by a known method, an n-side electrode 71 is formed on a predetermined region of the upper crat layer 63, and a p-side electrode 73 is formed on the back surface of the p-4np substrate 51, thereby obtaining the edge-emitting diode of the example. I can do it.

Note that the Zn diffusion layer and the light absorption portion 6 that constitute the portion M portion 67
The method for producing the ZnE scattering layer No. 9 in the same diffusion process is not limited to the above-mentioned method, and for example, the method described below may be used. FIG. 3 is a diagram for explaining this.

After the growth of the upper cladding layer 63 is completed, an n-InGaAsP cap layer 81, for example, is grown to a predetermined thickness on the upper cladding layer 63, and the light absorption portion 6 of this cap layer 81 is grown.
In this method, only the portion corresponding to 9 is selectively removed by a known method, and a diffusion mask is formed on this structure in the same manner as in the embodiment, and Zn diffusion processing is performed. In this case, the tip of the diffusion layer does not reach the active layer because the thickness of the semiconductor layer on the active layer is thicker than that of the spectral absorption part with a cap layer in the separation part formation plan head. The predetermined film thickness of the cap layer is shown in Fig. 2 (C)! This is the film thickness at which the same effect as creating a local film thickness difference can be obtained from the upper clamp layer described above.

Although the embodiments of the edge-emitting diode of the first invention and the method of manufacturing the edge-emitting diode of the second invention have been described above, these inventions are not limited to the above-mentioned embodiments. However, various changes can be made as described below.

For example, it is clear that the same effects as in the embodiment can be obtained even if the conductivity types of the substrate, each semiconductor layer, and the impurity in the above-described embodiment are reversed from those in the embodiment. Furthermore, the impurity used to form the impurity diffusion layer is not limited to Zn, but may be any suitable impurity (this can be changed).

Further, in the above-mentioned embodiment, the first and second inventions are 1nGaA
Although the present invention was applied to an edge-emitting diode of the sP/I-P system, it is clear that the present invention can also be applied to an edge-emitting diode (for example, a JGaAs-based one) constructed of Iya materials. It is power.

Furthermore, in the above-mentioned embodiments, the first and second inventions were applied to internal current confinement type edge-emitting diodes having V*, but these inventions apply to devices with other structures, such as those with different groove shapes, It is clear that this method can be widely applied to 8-day models and the like.

(Effects of the Invention) As is clear from the above description, according to the edge-emitting diode of the first invention of this application, the upper cladding layer, which was a leakage current path between the light-emitting part and the light-absorbing part, By providing a separation section consisting of an impurity diffusion layer of opposite conductivity type between the light emitting section and the light absorption section, the electric resistance is increased, so that the specific leakage current can be reduced even when there is no diffusion layer. Also,
Compared to the conventional H region, the M section of the present invention has a greater separation effect, so the separation section can be made smaller. In fact, conventionally 1
The M region, which used to be 50 um, is reduced to about 25 um in the embodiment of the present invention. Therefore, the edge-emitting diode can be made smaller.

Furthermore, in the light absorption section, each layer becomes a 111-type conductor due to the impurity diffusion layer, so that even if a leak current or flow occurs in the light absorption section, light emission does not occur, and therefore, the absorption coefficient does not decrease due to light emission. Roughly speaking, the absorption coefficient of the light absorption portion can be improved due to the light absorption effect of the impurity in the impurity diffusion layer. Therefore, the light absorption efficiency of the light absorption section is improved, so that even a light absorption section with a length of about 300 um (3/4 of the conventional length) can perform the desired light absorption and suppress oscillation.

In addition, since the active layers of the light emitting part and the light absorbing part can be continuous, there is no discontinuous surface between the light emitting part and the light absorbing region, which was a problem in the past, so there is no problem of internal reflection. .

Furthermore, according to the manufacturing method of the second invention, the impurity diffusion layer constituting the 1 minute M section and the impurity diffusion layer for increasing the absorption efficiency of the light absorption section can be formed in the same process. 1. The edge-emitting type guiot according to the invention can be easily manufactured.

[Brief explanation of drawings]

1(A) to (D) are diagrams for explaining the structure of an edge-emitting diode according to an example; FIGS. 2(A) to (C) are process diagrams for explaining an example of a manufacturing method; FIG. 3 is a diagram for explaining another embodiment of the manufacturing method, and FIG. 4 is an exploded perspective view for explaining the structure of a conventional edge-emitting diode. 51-p-I nP substrate 53-n-I nP current confinement layer 55-p-I nP current confinement layer 57-...groove 59-p-InP lower claride layer 6l-=p-I nGaAsP activity Layer 63-=n-I nP upper cladding layer 65...
Light emitting part, 67-69-... Light absorption part, 7]... N-side electrode 73.
-p side electrode

Claims (1)

[Claims] (1) A substrate of a first conductivity type, and a first conductivity type substrate formed on the substrate.
A light emitting section with a stripe structure and a light emitting section with a stripe structure for absorbing light generated from one end of the light emitting section on a base comprising a lower cladding layer of a conductivity type, an active layer, and an upper cladding layer of a second conductivity type. In an edge-emitting diode comprising a light-absorbing part, impurities of the first conductivity type are added to a portion of the base between the light-emitting part and the light-absorbing part to a depth that reaches the upper cladding layer from the surface of the part and does not reach the active layer. a separation part formed by diffusion, and an impurity of the first conductivity type is diffused into a part of the base corresponding to the light absorption part from the surface of the part to a depth reaching the active layer or a depth reaching the lower cladding layer. An edge-emitting diode characterized by: (2) a first conductivity type substrate and a first conductivity type substrate formed on the substrate;
A light emitting part with a stripe structure and a stripe structure with a stripe structure for absorbing light generated from one end of the light emitting part are formed on a base comprising a lower cladding layer of a conductivity type, an active layer and a lower cladding layer of a second conductivity type. an edge-emitting type diode comprising a light-absorbing part, wherein a first conductivity type is applied to a portion of the base between the light-emitting part and the light-absorbing part to a depth that reaches the upper cladding layer from the surface of the part and does not reach the active layer. a separation part formed by diffusing an impurity, and diffusing a first conductivity type impurity into a part of the base corresponding to the light absorption part from the surface of the part to a depth reaching the active layer or a depth reaching the lower cladding layer. In manufacturing an edge-emitting diode, the impurity of the first conductivity type is diffused according to the following (1) or (
2) A method for manufacturing an edge-emitting diode, characterized by carrying out the steps in step 2). (1) The film thickness of the part of the upper cladding layer corresponding to the light absorption part is made thinner than the film thickness of the part corresponding to the light emitting part and the light absorption part, and after that, the thickness of the part corresponding to the light absorption part of the upper cladding layer is made thinner than the film thickness of the part corresponding to the light absorption part. A first conductivity type impurity is introduced. (2) A thin film is formed on a portion of the upper cladding layer corresponding to between the light emitting part and the light absorption part, and then a first conductivity type impurity is introduced into the base from above the upper cladding layer.