JPH0542837B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device having a light-emitting element and a light-receiving element on one substrate, that is, a method for manufacturing a light-emitting and light-receiving element.

In a conventional general optical communication method using an optical fiber, light emitted from a light emitting element is transmitted through the optical fiber, and the light is collected and received on a light receiving element.
In order to carry out bidirectional communication in this method, two sets of systems each consisting of a light emitting element, an optical fiber, and a light receiving element are required, which makes the system extremely expensive. To solve this problem, a light-emitting and light-receiving element having both light-emitting and light-receiving functions is required.

As a conventional light-emitting light-receiving element, there is one in which a part of the active layer of a general light-emitting element is separated from the light-emitting element portion and used as a light-receiving element by applying a reverse bias. FIG. 1 is a schematic cross-sectional view of a light emitting and receiving element having such a structure. (However, in this figure and the following figures, the substrate and the growth layer are drawn without hatching). In the figure, 1 is an n ⁺ -InP substrate,
2 is n ⁺ -InP layer, 3 is n-InGaAsP layer, 4 is p ⁺ -
InP layer, 5 is an insulating film, 6 is a p-side electrode of the light-receiving element, 7 is a p-side electrode of the light-emitting element, and 8 is a light-shielding part that prevents light leaking from the light-emitting element from entering the light-receiving element. , 9 is an n-side electrode. In this light emitting light receiving element, both the light emitting element part 10 and the light receiving element part 11 are n-
A pn junction is formed by the InGaAsP layer 3 and the p ⁺ -InP layer. Incidentally, a light-emitting light-receiving element equipped with a blocking section 8 has already been proposed by the inventor of the present invention, and a patent application has been filed (Japanese Patent Application No. 178828-1982).

Next, an example of a method for manufacturing the light emitting/receiving element shown in FIG. 1 will be described. FIGS. 2a to 2d are schematic cross-sectional views of semifinished products produced in each intermediate step of this manufacturing method.
n ⁺ -InP layer 2 (impurity concentration 1) ^as a buffer layer on ^{n +} -InP substrate 1 (impurity concentration 1
x10 ¹⁸ cm ^-3 ) to approximately 4 μm, n-InGaAsP layer 3 (impurity concentration 1×10 ¹⁷ cm ^-3 , photoluminescence peak wavelength 1.3 μm)
m) is approximately 2 μm, p ⁺ -InP layer 4 (impurity concentration 1×
10 ¹⁸ cm ^-3 ) was grown to a thickness of approximately 2 μm [Figure a], and then processed through a photoresist treatment process, etc.
Etch in a ring shape until reaching the n ⁺ -InP layer 2 [Figure b], then CVD- as the insulating film 5.
A SiO ₂ film of 2500 Å is formed [Figure c]. After that, the p-side electrode 6 of the light-receiving element part, the p-side electrode 7 of the light-emitting element part, and the light shielding part 8 are simultaneously formed using an AuZn alloy electrode as a p-side electrode and a Ti/Pt/Au multilayer structure of its bonding pad. do. After that, the total thickness was made 60 μm by back polishing, and AuGe was applied to the n ⁺ −InP substrate side.
The n-side electrode 9 is formed of an alloy electrode of 1 and a bonding pad of Au [FIG. d].

The light-emitting light-receiving device manufactured by this manufacturing process example has n-
The same growth layer is used for the InGaAsP layer 3 and the n-InGaAsP layer 3 which is the light absorption layer of the light receiving element section 11. However, the active layer requires 1 for high-speed operation.
An impurity concentration of about ×10 ¹⁷ or more is required, and the other light absorption layer preferably has an impurity concentration of about 1×10 ¹⁶ or less. The composition of the light-emitting and light-receiving elements described with reference to FIGS.
Only about 0.4 μm can be obtained. When the depletion layer width is small in this way, the light receiving element section 11 has disadvantages such as slow operation speed, low sensitivity, and large dark current due to tunnel current in terms of current-voltage characteristics. Therefore, the light-receiving element section 11 of the light-emitting light-receiving element shown in FIG. 1 had poor frequency characteristics of pulse response. Further, in order to increase the speed of the light emitting element section 10, it is necessary to make the active layer thinner, but this also has the problem of being contradictory to increasing the speed and sensitivity of the light receiving element section. As described above, in the conventional method of manufacturing a light emitting and receiving element, it has not been possible to optimize the characteristics of both the light emitting element and the light receiving element.

The purpose of the present invention is to eliminate such drawbacks of the prior art,
An object of the present invention is to provide a method for manufacturing a light emitting light receiving element, which allows optimization of both the light emitting element part and the light receiving element part, and satisfies high light emitting efficiency, high light receiving sensitivity, and fast response speed at the same time.

The method for manufacturing a light emitting/receiving element of the present invention includes: forming a first semiconductor layer having a first conductivity type and having a forbidden band width E1;
Indicates the first conductivity type impurity concentration N1 and the forbidden band width E2
a second semiconductor layer of (E1>E2), a third semiconductor layer of the first conductivity type and a forbidden band width E3 (E3>E2);
A step of forming a fourth semiconductor layer having a first conductivity type impurity concentration N2 (N2>N1) and a forbidden band width E4 (E4≦E2) and a step of removing a partial region until reaching the third semiconductor layer and forming a recessed portion. a step of changing the conductivity type to a second conductivity type until the second semiconductor layer in the recess is reached; a step of removing the outer periphery of the recess until it reaches the first semiconductor layer; and the recess and the recess. and a step of individually forming electrodes on the separated outer periphery.

Next, the present invention will be explained in detail with reference to the drawings.
FIG. 3 is a schematic cross-sectional view of a light-emitting light-receiving device obtained according to an example of the present invention. In the figure, 33
is n ⁺ -InP layer, 34 is n ^- -InGaAsP layer, 36 is p ⁺
-InP layer, 37 is an insulating film, 38 is p of the light receiving element part
side electrode, 39 is a p-side electrode of the light emitting element section, 40 is a light shielding section, 41 is a light emitting element section, 42 is a light receiving element section, 4
3 indicates an n-side electrode of the light-receiving element section, and 44 indicates an n-side electrode of the light-emitting element section. In the device to which the present invention is applied, n-InGaAsP3 is used for the active layer of the light-emitting element section 41, and n ^-- InGaAsP34 is used for the light absorption layer of the light-receiving element section 42, thereby reducing the concentration of both. It has become possible to optimize each element.

In order to explain an example of the manufacturing method of the above embodiment, schematic cross-sectional views of semi-finished products manufactured by the manufacturing method of this embodiment are shown in FIGS. 4a to 4c. n ⁺ -InP layer 2 as a buffer layer on n ⁺ -InP substrate 1 (impurity concentration 1×
10 ¹⁸ cm ^-3 ) is about 4 μm, the n-InGaAsP layer 3 (impurity concentration 1×10 ¹⁷ cm ^-3 photoluminescence peak wavelength 1.3 μm) as the active layer of the light emitting element is about 2 μm, and n ⁺ -InP
The layer 33 (impurity concentration: 1×10 ¹⁸ cm ^-3 ) is approximately 2 μm thick, and the n ⁻ −InGaAsP layer 3 serves as a light absorption layer in the light receiving element portion.
^{[ _} _{_} ^{_ _} After photoresist treatment, etching is performed until the n ⁺ -InP layer 33 is reached, forming a concave portion (FIG. 4b). Then, by using the Cd thermal diffusion method, a region with a depth of approximately 2 μm, which is shown by placing dots in b in this figure, is defined as p ⁺ .
Then, by photoresist treatment etc., the center of the circular recess is aligned, and the inner diameter is 30 μm.
Then, a ring shape having an outer diameter of 50 μm is removed and separated into a light emitting element section 41 and a light receiving element section 42. Thereafter, a CVDSiO ₂ film with a thickness of 2500 Å is formed as the insulating film 37, and the p-side electrode 38 of the light-receiving element section 42, the p-side electrode 39 of the light-emitting element section 41, and the light shielding section 40 are formed by vacuum evaporation of Ti/Pt/Au. After the photoresist processing step, the position is aligned centering on the recessed part, and the outer peripheral part other than the circular part with a diameter of 300 μm is removed until it reaches the n ⁺ -InP layer 33, and the light receiving element part 4 is formed by vacuum evaporation of AuGe.
2 n-side electrodes 43 are formed. Thereafter, the n ⁺ -InP substrate 1 side is polished to a wafer thickness of approximately 60 μm, and the n-side electrode 44 of the light emitting element portion 41 is coated with AuGe by vacuum evaporation.
was formed. This embodiment manufactured by the above manufacturing method can improve the characteristics of the light receiving element part 42 while keeping the light emitting element part 41 the same as the conventional one, compared to the conventional light emitting light receiving element.

As an example of improvement, Fig. 5 shows the current-voltage characteristics of an element obtained by the conventional manufacturing method (hereinafter referred to as the conventional element) and an element obtained by this example (hereinafter referred to as the element of the present invention). show. In this figure, the current-voltage characteristic line of the light-receiving element part 11 of the conventional light-emitting light-receiving element shown in FIG. Indicated. It can be seen from both of these characteristic lines 50 and 51 that the dark current of the light emitting/receiving element according to the present invention is reduced compared to the conventional element. This is because the generation of tunnel current is suppressed by reducing the impurity concentration of the light absorption layer in the light receiving element portion.

Further, FIG. 6 shows a pulse response waveform for a solitary pulse with a bit rate of 32 Mb/S, a duty of about 1/2, a mark rate of 1/2, and a wavelength of 1.3 μm. The pulse response waveform of the light receiving element section 11 of the conventional light emitting light receiving element is indicated by reference numeral 60, and the pulse response waveform of the light receiving element section 42 of the embodiment is indicated by reference numeral 61. according to this,
In the conventional element, the pulse response wave has a triangular shape and small amplitude, but in the embodiment, the waveform approaches the optical input (rectangular wave), that is, the frequency characteristics of the pulse response are good, and the amplitude is large. ing. This is the effect of reducing impurity concentration,
In the conventional device, the depletion layer width could only be expanded to about 0.4 μm, but in the device of the present invention, it can be expanded to about 4 μm. In contrast, in the device of the present invention, most of the carriers were generated within the depletion layer, and the slow diffusion current component was reduced. Additionally, the AC quantum efficiency has also been improved and the amplitude has become larger.

In the above embodiments, InP/InGaAsP-based elements were explained, but other three types such as InGaAs and AlGaAs can also be used.
It is clear that primary or quaternary materials may be used.
In the embodiment, the conductivity type of the active layer 3 of the light-emitting element part 41 and the light absorption layer 34 of the light-receiving element part 42 is n-type, but the present invention is effective even if the conductivity types are p-type or different. Also, both have the same composition.
Although InGaAsP was used, it is also effective to use a different composition or material. Furthermore, the element shape and electrode shape in the examples are not limited to these.

According to the present invention, as described above, it is possible to provide a method for manufacturing a light emitting and receiving element that can optimize the characteristics of both the light emitting element and the light receiving element.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a light-emitting light-receiving device produced by a conventional manufacturing method, FIGS.
The figure is a schematic sectional view of one embodiment of the present invention, FIG.
~c is a schematic cross-sectional view of a semi-finished product made in the manufacturing process of an element according to this manufacturing method, and FIG. 5 is a current-voltage diagram of the conventional light-emitting light-receiving element shown in FIG. 1 and the light-receiving element part in the embodiment shown in FIG. The characteristic diagram, FIG. 6, is a pulse response waveform diagram of the light receiving element section. 1... n ⁺ -InP substrate, 2... n ⁺ -InP layer, 3...
...n-InGaAsP layer, 4...p ⁺ -InP layer, 5,37
... Insulating film, 6, 38 ... P-side electrode of light-receiving element section, 7, 39 ... P-side electrode of light-emitting element section, 8, 4
0... Light shielding part, 9... N-side electrode serving both as light emitting element part and light receiving element part, 10, 41... Light emitting element part, 1
1, 42... Light receiving element section, 33... n ⁺ -InP layer,
34...n ^-- InGaAsP layer, 35...n-InP layer,
36... p ⁺ region formed by thermal diffusion method, 4
3...n-side electrode of the light-receiving element section, 44...n-side electrode of the light-emitting element section.

Claims (1)

[Claims] 1. On a first semiconductor layer having a first conductivity type and a forbidden band width E1, a second semiconductor layer of the first conductivity type and having an impurity concentration N1 and a forbidden band width E2 (E1>E2);
A third semiconductor layer of the first conductivity type and a forbidden band width E (E3>E2), a third semiconductor layer of the first conductivity type and an impurity concentration N2 (N2<
N1) and the fourth forbidden band width E4 (E4≦E2)
a step of forming a recess by removing a partial region until reaching the third semiconductor layer; and a step of forming a recess by removing a partial region until reaching the second semiconductor layer of the recess
a step of removing the outer periphery of the recess until it reaches the first semiconductor layer; and a step of forming electrodes individually in the recess and the outer periphery separated from the recess. A method for manufacturing a light-emitting light-receiving element, characterized in that: