JPH0220853Y2 - - Google Patents

Description

[Detailed Description of the Invention] <<Field of the Invention>> The present invention relates to a light-emitting and light-receiving element that has both light-emitting and light-receiving functions, and is an improvement of the light-emitting and light-receiving element that is suitable for use in bidirectional optical communication using a single optical fiber. Regarding.

<<Prior art and its problems>> The present inventor has already proposed a structure shown in FIG. 1 as this type of light-emitting light-receiving element.

That is, the collector layer 2 is formed on the main surface of the semiconductor substrate 1.
and forming a base layer 3, forming a recess 21 reaching the substrate 1 in the center of the base layer 3, forming an emitter/cathode layer 4 as a cladding layer in the base layer 3 including the recess 21, Recessed part 21
An annular separation groove 22 surrounding the substrate 1 is formed with a depth that reaches the substrate 1, and a light emitting layer 5 and an anode layer 6 are formed to be laminated within the area surrounded by the separation groove 22, thereby forming the light emitting element section 100. In addition, the outer region of the separation groove 22 is configured as a light emitting element portion 200, for example, a phototransistor.

Note that numerals 7, 8, and 9 are a common electrode formed on the substrate 1, an anode electrode of the light receiving element section 200, and an anode electrode of the light emitting element section 100.

In such a light-emitting light-receiving element, the base layer near the recess 21 constitutes a current confinement layer 23 that narrows the current path of the light-emitting element section 100, so the portion of the light-emitting layer 5 corresponding to the recess 21, for example, The recombination efficiency of the carriers at the center of the optical fiber increases, and light is emitted with a small emission diameter, making it possible to effectively couple light to the optical fiber.

However, in the light-emitting and light-receiving device configured in this way, the current confinement layer 23 of the light-emitting device section 100 and the base layer 3 of the light-receiving device section 200 have the same thickness, but the thickness of the current confinement layer 23 is as described below. For some reason, it is necessary to make it sufficiently thick compared to the diffusion length of minority carriers.

That is, when the light emitted from the light emitting layer 5 reaches the current confinement layer 23, if the current confinement layer 23 is made of, for example, a p-GaAs layer, the current confinement layer 23
electron-hole pairs are likely to be generated. Moreover, since the diffusion length of electrons is long, when the current confinement layer 23 is thin, electrons flow to the outside without being recombined with holes, and a large number of holes are accumulated in the current confinement layer 23.

As a result, the current confinement layer 23 becomes biased in the forward direction with respect to the collector layer 2 and the emitter/cathode layer 4, and the potential barrier becomes low, which tends to reduce the current confinement effect.

On the other hand, in the light receiving element section 200, in order to obtain a large gain, the thickness of the base layer 3 needs to be sufficiently thin compared to the diffusion length of minority carriers.

That is, the amplification factor of the light receiving element section 200 is expressed as β=1/cos h(W _B /L)−1. Here, β is the current amplification factor, W _B is the thickness of the base layer 3, and L is the diffusion length of minority carriers. As can be seen from this equation, in order to increase the amplification factor of the light receiving element section 200, it is preferable to make the thickness of the base layer 3 sufficiently thin compared to the minority carrier diffusion length.

In this manner, in the case of a light emitting light receiving element, the conditions for obtaining the light emitting element section 100 with a high degree of coupling to the optical fiber and the light receiving element section 200 with high sensitivity are contradictory.

<<Purpose of the invention>> The present invention was made under these circumstances, and aims to provide a light-emitting element with good coupling to an optical fiber and good light-receiving sensitivity.

<<Configuration and Effects of the Invention>> In order to achieve this object, the present invention includes a light emitting element portion formed on the main surface of a semiconductor substrate, and a light emitting element portion formed on the main surface of the semiconductor substrate with an annular separation groove in between. a light-receiving element portion formed on the surface; and a common layer forming a current confining means for narrowing the current path of the light-emitting element portion in the light-receiving element portion and forming a light-receiving layer in the light-receiving element portion. In the light-emitting light-receiving device, the thickness of the common layer in the light-emitting element portion is formed to be thicker than the thickness of the common layer in the light-receiving element portion.

According to such a configuration, the coupling efficiency with the optical fiber in which the function of the current confinement means in the light emitting element portion is fully exerted is improved, and the sensitivity in the light receiving element portion is also increased.

<<Description of Examples>> The details of the present invention will be described below. Note that parts common to the light emitting light receiving element shown in FIG. 1 are given the same reference numerals.

FIG. 2 is a cross-sectional view showing one embodiment of the light emitting and receiving element according to the present invention, in which a light emitting element section is exemplified by stacked LEDs, and a light receiving element section is a phototransistor.

In FIG. 2, a collector layer 2 and a base layer 3 are formed on the main surface of a semiconductor substrate 1, and a recess 2 reaching the substrate 1 is formed in the center of the base layer 3.
1 is formed.

The base layer near the recessed portion 21 is thicker than other portions, as will be described later, and constitutes a current confinement layer 23 as a current confinement means of the light emitting element portion 100, which will also be described later.

The base layer 3 including the recessed portion 21 has emitters.
A cathode layer 4 is formed, and a separation groove 22 is formed in the emitter cathode layer 4 so as to surround the recess 21.
is formed, and this separation groove 22 has a depth that reaches at least the collector layer 2.

In the region surrounded by the separation groove 22, a light emitting layer 5 and an anode layer 6 are laminated and formed,
A part of the light emitting element section 100 is configured.

Furthermore, a portion surrounding the light emitting element section 100 with the separation groove 22 in between is a light receiving element section 200 .

Note that numerals 7, 8, and 9 are a common electrode formed on the substrate 1, an anode electrode formed on the light receiving element section 200, and an anode electrode formed on the light emitting element section 100.

Then, the light emitting element section 100 and the light receiving element section 2
In 00, the current confinement layer 23 and the base layer 3 are a common layer, and the current confinement layer 23 is thicker than the base layer 3. In other words, the thickness of the common layer in the light emitting element section 100 is formed sufficiently thicker than the diffusion length of minority carriers, and the thickness of the common layer in the light receiving element 200 is formed sufficiently thinner than the diffusion length of minority carriers.

The light emitting/receiving device configured as described above is manufactured as follows.

First, as shown in ^FIG .
A non-doped n ^- -GaAs layer as the collector layer 2 and a Ge-doped p-GaAs layer as the base layer 3 are laminated to a thickness of approximately 3 μm and 5 μm, respectively.

Next, using a sulfuric acid-hydrogen peroxide based etching solution, as shown in FIG.
Etch to the following thickness. On the other hand, at least p-
A recess 21 having a diameter of about 30 μm and having a depth penetrating the GaAs layer 3 is formed by etching.

Next, as shown in FIG. 5, an n-type emitter/cathode layer 4 is formed on the main surface of the material processed as described above by liquid phase epitaxial growth.
_{-Ga0.7Al0.3As layer} , p- _Ga0.3 as the light emitting layer _{5 .
95} Al ₀ . ₀₅ As layer and p-Ga ₀ as the anode layer 6.
₇ Al ₀ . ₃ As layers are laminated with film thicknesses of approximately 7 μm, 1 μm, and 3 μm, respectively.

In this way, for the five-layer laminated substrate 1,
The above-mentioned recessed part 2 is formed using a photolithography.
A separation groove 22 having a width of about 10 to 20 μm and reaching at least the n ^- -GaAs layer 2 is formed by etching so as to surround the n - -GaAs layer 2 .

Furthermore, _{the p-Ga 0.7 Al 0} .
₃ As _{layer 6 and p-Ga 0.95 Al 0.05} As layer ₅ are removed by etching.

After that, for the p-GaAIAs layer 4, Au-Zn
For the n-GaAs layer and the GaAlAs layer, an Au-Ge alloy is vapor-deposited and shaped into a desired shape to form each anode electrode 8, 9, which emits light and receives light as shown in FIG. The element is completed.

In the light-emitting/receiving element of the present invention, when the common electrode 7 is biased negatively and the anode electrode 9 of the light-emitting element section 100 is biased positively, the p-Ga _0.95 Al _0.05 As layer ₅ emits light as a light-emitting layer _. do. In this case, the current confinement layer 2
Since the thickness of 3 is thicker than the diffusion length of the minority carrier,
The current confinement layer 23 constricts the current in the light emitting element section 100 without lowering the potential barrier. Therefore, the light emitting portions of the light emitting layer 5 are concentrated in the portion corresponding to the recessed portion 21, so that the coupling efficiency with the optical fiber can be maintained high.

Further, when the common electrode 7 is biased positively and the anode electrode 8 of the light receiving element section 200 is biased negatively, the light receiving element section 200 operates as a light receiving element. in this case,
Since the thickness of the base layer 3 is sufficiently thinner than the diffusion length of the minority carriers, an amplification factor of several tens to several hundreds can be obtained, making it possible to increase the sensitivity.

In addition, in the above-mentioned embodiment, an example of an element using GaAs-based material was shown, but for example, InGaAs-based material is used.
It is also possible to implement the method in the same manner when using a system material.

Further, in the above embodiment, a case was explained in which a phototransistor was used as the light receiving element, but in the light emitting light receiving element according to the present invention, the thickness of the common layer forming the light receiving layer of the light receiving element is a diffusion of minority carriers. Since it is formed thinner than it is long, it can be implemented satisfactorily even when used as a photodiode.

That is, according to the configuration of the present invention, since the light-receiving layer is formed to be thinner than the diffusion length of minority carriers, it is possible to suppress the probability that carriers generated in the light-receiving layer become reactive current components. A photodiode can also be used as the light receiving element section.

[Brief explanation of drawings]

FIG. 1 is a reference sectional view related to the light emitting and receiving device of the present invention, FIG. 2 is a sectional view showing an embodiment of the light emitting and receiving device of the present invention, and FIGS. 3 to 5 are the light emitting devices shown in FIG. FIG. 3 is a process diagram showing a method for manufacturing a light receiving element. 1...Substrate, 100...Light emitting element section, 200...
... Light receiving element portion, 22 ... Separation groove, 23 ... Common layer (current confinement means), 3 ... Common layer (base layer), 5
...Light-emitting layer.

Claims (1)

[Scope of utility model registration request] A light emitting element section is provided on the main surface of the semiconductor substrate, a light receiving element section is provided on the outer circumferential side of the light emitting element section with an annular separation groove in between, and current confinement means narrows the current path of the light emitting element section. , and a light-emitting element part in which the base layer constituting the light-receiving layer of the light-receiving element part is formed of a common layer, the thickness of the common layer being thicker than the diffusion length of minority carriers in the light-emitting element part; . A light-emitting light-receiving element, wherein the light-receiving element portion is formed to be thinner than the diffusion length of minority carriers.