JPH06260673A - Semiconductor photodetector and manufacture thereof - Google Patents

Abstract

PURPOSE:To eliminate a malfunction of a semiconductor photodetector due to reflection of a background light. CONSTITUTION:An InGaAs light absorption layer 2c is formed in a small region of several mum in size, disposed entirely on an n'' type InP substrate 1, buried between the small regions 2c, an InP crystalline layer 3c having a wide forbidden band width is grown thereon until it becomes a predetermined thickness, and a p-type region 7 is so farmed by diffusing as to reach part of the layer 2c in the layer 3c of a photoreceiving region. Thus, carrier generated by a background light absorbed by the region 2c cannot move externally by the region 2c, but extincts by itself. As a result, deterioration of detected frequency characteristics due to the background light can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light receiving element used for optical communication and a method of manufacturing the same, and more particularly to a semiconductor light receiving element capable of preventing background light which causes deterioration of frequency response.

[0002]

2. Description of the Related Art FIG. 6 shows a structure of an example of a conventional semiconductor light receiving element. In the figure, 1 is an n ⁺ -InP substrate, 2a is an n ⁻ -InGaAs light absorption layer having a thickness of about 2 μm formed on the n ⁺ -InP substrate 1, and 3a is the n ⁻ -InGa.
It is an n ⁻ -InP window layer having a thickness of about 1 μm or more formed on the As light absorption layer 2a. 4 is the n ^-- InP window layer 3a
Approximately 4000 angstroms of S formed on top
The iN insulating film 7 is a Z formed in the n ⁻ -InP window layer 3a so as to extend to the n ⁻ -InGaAs light absorption layer 2a.
P ⁺ regions 5 by n-impurity diffusion are connected to the P ⁺ regions 7 and are provided with an A-thickness of about 3000 Å.
u is a cathode electrode, 6 is the n ⁺ -InP substrate 1
An anode electrode made of Au and having a thickness of about 3000 angstroms, which is connected to, is a metal mask 8 provided in a region other than the light receiving region of the present device for blocking background light.

FIG. 7 shows the structure of another example of the conventional semiconductor light receiving element. In FIG. 7, 2b is n ^-- I of the above-mentioned conventional example 1.
n ^-- InGaAs corresponding to the nGaAs light absorption layer 2a
The light absorption layer is provided only in a portion corresponding to the light receiving area. 3b is the n ⁻ -InP window layer 3a of the above-mentioned conventional example 1.
Corresponding to the n ⁻ -InP window layer, which is the above n ^{− −}
-It is provided as a buried layer for burying the InGaAs light absorption layer 2b. Further, in Conventional Example 2, the metal mask 8 of Conventional Example 1 is not provided.

Next, a procedure for manufacturing the semiconductor light receiving element of the first conventional example shown in FIG. 6 will be described. First, vapor phase epitaxy on the InP substrate 1
By law or the ^like, n - -InGaAs layer ^2a, n - -InP
Layers 3a are grown in succession and are shown in these layers,
An insulating film (not shown) having an opening slightly larger than that of the SiN insulating film 4 to be formed later is formed, and Zn diffusion is selectively performed using this as a mask to form the P ⁺ diffusion region 7. Next, SiN insulating film 4, cathode electrode 5,
The metal mask 8 and the anode electrode 6 are formed by plasma CVD,
It is formed using a vacuum vapor deposition device.

Next, a procedure for manufacturing the semiconductor light receiving element of the second conventional example shown in FIG. 7 will be described. First, on the InP substrate 1, V
An n ^-- InGaAs layer (2a in FIG.
Are formed with a uniform thickness, and the n ^-- InGaAs layer 2b corresponding to the region to be diffused in the subsequent step is left, and the others are removed by etching. Thereafter, ⁿ by a liquid phase epitaxial (LPE) growth method - the -InP layer 3b, n ^- -
The growth is performed so as to fill the InGaAs layer 2b. However, when InP is grown on InGaAs by the LPE method, InGaAs is melted by InP, and meltback occurs.
InGaAsP having a composition intermediate between these is usually sandwiched between GaAs and InP. The subsequent steps such as electrode formation are the same as those in FIG. However, in Conventional Example 2, the metal mask 8 is not formed.

Next, the operation of the semiconductor light receiving elements of the conventional examples 1 and 2 will be described. Here, the basic operations of the conventional examples 1 and 2 are the same. First, the cathode electrode 5 and the anode electrode 6
A positive voltage on the anode side, that is, a reverse bias voltage to the pn junction between the P ⁺ diffusion region 7 and the n ⁺ -InP substrate 1, is applied from the upper portion of the P ⁺ diffusion region 7. When light with a wavelength of 1.0 to 1.6 μm is incident, the light passes through the n ⁻ -InP layers 3a and 3b (P ⁺ diffusion region 7), respectively, ^and forms a carrier pair in the n ⁻ -InGaAs layers 2a and 2b. The holes are separated from the electrons according to the electric field in the n-InGaAs layer to generate a photovoltage. Thereby, in the output circuit between the cathode electrode 5 and the anode electrode 6,
Photocurrent in response to the optical signal will flow. Such semiconductor light receiving elements of Conventional Examples 1 and 2 are usually used to detect the monitor light of the semiconductor laser device and control the optical output of the semiconductor laser device accordingly.

Next, a method of preventing background light in these conventional devices will be described. The deterioration of the frequency characteristic due to the background light is caused by the light absorption in the light absorption layers 2a and 2b other than the P ⁺ diffusion region 7, and the generated carriers are delayed by diffusion to delay P ^+.
It is caused by reaching the area 7. Therefore, in the conventional example 1 of FIG. 6, the metal mask 8 is formed on the surface other than the P ⁺ region 7, by reflecting the background light by the metal mask 8, also in the conventional example 2 of FIG. 7, the P ⁺ region 7 The light absorption layer 2b other than the above is removed to form the n ⁻ -InP layer 3b so as to embed the light absorption layer 2b, and the background light is transmitted therethrough to prevent the deterioration of the frequency characteristic of the light detection sensitivity. ing.

[0008]

Since the conventional semiconductor light receiving element is constructed as described above, in the prior art example 1, the background light is reflected by the metal mask 8 to become the return light, and this background light is the above-mentioned light. When returning to the monitor light output section of the semiconductor laser device, there is a problem that the operation of the laser device is affected and the laser output light is also adversely affected.

In the second conventional example, the background light is the substrate 1
The light may pass through the inside and be reflected by the anode electrode 6, which may cause deterioration of the photodetection frequency characteristic of the light receiving element.
However, there is a problem that it is difficult to align the position with the P ⁺ diffusion region 7.

The present invention has been made in order to solve the above-mentioned problems, and by absorbing all background light and immobilizing generated carriers without using a metal mask for reflecting light, It is an object of the present invention to provide a semiconductor light receiving element capable of preventing the deterioration of the light detection frequency characteristic of the light receiving element and eliminating the difficulty of aligning the diffusion region, and a manufacturing method thereof.

[0011]

A semiconductor light-receiving element according to the present invention has a crystal layer serving as a light-absorbing layer having a small area of several μm square and spread over the entire main surface of a semiconductor substrate. In order to bury the gap region and to have a certain thickness, a crystal layer having a wider forbidden band than the light absorption layer is buried and formed thereon.

Further, according to the present invention, the plurality of small area light absorption layers are formed on the entire surface of the semiconductor substrate.

Further, according to the present invention, the semiconductor substrate is an n-type I-type.
nP substrate, the plurality of light absorption layers are n-type InGaAs layers,
The buried layer is an n-type InP layer, and a p-type diffusion region is formed on the plurality of light absorption layers and the buried layer.

A method of manufacturing a semiconductor light receiving element according to the present invention comprises a step of forming a crystal layer to be a light absorption layer with a uniform thickness on a main surface of a semiconductor substrate, and a crystal layer to be the light absorption layer. , A step of dividing and forming into a plurality of light absorption layers having a small area by etching using a lattice-shaped mask pattern, and filling a gap area between the light absorption layers of the plurality of small areas by a liquid phase epitaxial method. And a step of burying and growing a crystal layer having a wider forbidden band than that of the light absorbing layer until a constant thickness is formed on the light absorbing layer, The step of forming a diffusion region forming a pn junction with them so as to reach a part of the lower light absorption layer is included.

[0015]

In the semiconductor light receiving element according to the present invention, since the light absorption layers in the plurality of small areas are evenly present on the wafer and these are separated by the barrier layer made of a crystal having a wide forbidden band width, the light absorption layers other than the diffusion area are formed. Carriers generated by the background light absorbed in the light absorption layer region cannot move outside the small region and spontaneously disappear. Therefore, in Conventional Example 1,
The background light is reflected by the metal mask and becomes return light, which adversely affects the operation of the semiconductor laser device and, by extension, the laser output light, and the background light in Conventional Example 2 is transmitted through the substrate and the anode electrode. It is possible to solve the problem that the photodetection frequency characteristic of the light receiving element is deteriorated due to the reflection by the laser beam, or the alignment of the InGaAs light absorption layer and the P ⁺ diffusion region is difficult in the production thereof.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. Example 1. FIG. 1 shows the structure of a semiconductor light receiving element according to the first embodiment of the present invention. In the figure, the same symbols as those in FIGS. 6 and 7 indicate the same components. In FIG. 1, 2c is several μm (2
～3Myuemu) separated in the region of the small area of square size n ^- -
The InGaAs light absorption layer has a height of about 2 μm. 3c is formed so as to fill the gap region between the n ⁻ -InGaAs light absorption layers 2c in these small regions, and is formed on the upper layer thereof with a thickness of about 1 μm or more. It is an n ^-- InP layer made of InP having a large band width. Reference numeral 7 denotes a P ⁺ diffusion region formed so as to extend from the upper surface of the n ⁻ -InP layer 3c to the n ⁻ -InGaAs light absorption layer 2c in the small region,
The diameter is formed to about 20 to 30 μm. Figure 2
Is the InGaAs light absorption layer 2c in the small region, the n ^-- InP layer 3c formed in the gap region between them, and P ⁺
A top view of the diffusion region 7 is shown.

Next, a method of manufacturing the semiconductor light receiving element of the first embodiment will be described with reference to FIG. First, the semiconductor substrate n
On the main surface of the ⁺ -InP substrate 1, an n ⁻ -InGaAs layer 2 serving as a light absorption layer is formed with a uniform thickness by the VPE growth method or the like (FIG. 3 (a)).

Next, the entire surface of the wafer thus formed is etched by using a grid pattern as shown in FIG. 2 to form a plurality of small regions of the InGaAs light absorption layer 2c.
Are formed (FIG. 3 (b)).

After that, the InP layer 3c is grown by the LPE method so as to fill the gap between the small region InGaAs layers 2c and subsequently to have a predetermined thickness on the small region InGaAs layer 2c. (Fig. 3 (c)). The subsequent steps of forming the P ⁺ diffusion region 7 (FIG. 3 (d)) and forming the electrodes are the same as those in the conventional method.

The basic operation of this embodiment is similar to that of the conventional example, but in this embodiment, the InGaAs light absorption layer 2c in a small region is evenly present on the wafer, and these have a wider forbidden band. The light absorption small region 2 other than the P ⁺ diffusion region 7 is separated by the barrier layer 3c made of InP.
The carriers generated by the background light absorbed by c cannot move to the outside of the small region 2c and will spontaneously disappear. Therefore, in Example 1 in which the metal mask is not used, the background light in the conventional example 1 is reflected by the metal mask 8 and becomes return light, which adversely affects the monitor output light and eventually the laser output light. It can be resolved. Further, in the conventional example 2, the background light is transmitted through the substrate 1 and reflected by the anode electrode 6 and is also detected, which causes deterioration of the detection frequency characteristic. Further, the background light is diffused with the embedded InGaAs layer 2b. It is possible to solve the problem that it is difficult to align the position with the region 7. Therefore, it is possible to prevent the background light in the semiconductor light receiving element by a simple manufacturing method, and it is possible to obtain the semiconductor light receiving element in which the frequency characteristics are not deteriorated by the background light.

Example 2. 4 (a) to 4 (d) show the second embodiment of the present invention.
FIG. 6 is a diagram showing a method for manufacturing a semiconductor light receiving element according to the example of FIG. According to the manufacturing method of the first embodiment, the n ⁺ -InP substrate 1
After forming the n ⁻ -InGaAs layer 2 to be the light absorption layer with a uniform thickness on the main surface of the substrate (FIG. 3 (a)), this was etched using a grid pattern as shown in FIG. To form a plurality of small regions of the light absorption layer 2c (FIG. 3 (b)), and then to fill the gap between the InGaAs small regions 2c.
Although the nP layer 3c is grown (FIG. 3C), in the second embodiment, after the InGaAs layer 2 serving as the light absorption layer is formed to have a uniform thickness, the InGaAs layer is embedded and grown later. I that is a crystal that is not melted back by InP
The nGaAsP layer 9 is thinly formed to a thickness of 0.1 to 0.3 μm (FIG. 4 (a)), and thereafter, etching is performed using the above-mentioned lattice pattern to form the light absorption layer 2c in a small area. (FIG. 4 (b)), and thereafter, as shown in FIG. 4 (c), a gap between the InGaAs small regions 2c is buried and grown by an InP crystal 3c, and thereafter, a P ⁺ diffusion region 7 is similarly formed ( FIG. 4D) is performed to form a semiconductor light receiving element.

In the second embodiment as described above, the upper surface of the InGaAs light absorption layer 2c is formed by the InGaAsP layer 9 which is a crystal that is not melted back by InP.
Meltback can be prevented by the InP layer 3c that fills and grows the gap region between the InGaAs small regions 2c.

Example 3. 5 (a) to 5 (d) show the third embodiment of the present invention.
FIG. 6 is a diagram showing a method for manufacturing a semiconductor light receiving element according to the example of FIG. The third embodiment is the same as the first embodiment, except that the light absorption layer region 2c is formed by etching using a grid pattern (FIG. 3B), and then InP is formed in the gap region between the InGaAs small regions 2c. Layer 3c is embedded and grown (FIG. 3C).
) Before, as shown in FIG. 5 (b), the plurality of InGaA
The InGaAs is formed on the upper surface and side surfaces on the small region 2c of s.
InGaAsP layer 9 which is a crystal that does not melt back
Is thinly formed to a thickness of 0.1 to 0.3 μm, and then
As shown in FIG. 5C, the InP layer 3c is embedded and grown in the gap region between the InGaAs small regions 2c.

In the third embodiment as described above, InGa
Due to the InGaAsP layer 9 which is a crystal that does not melt back As, the upper surface and the side surface of the InGaAs light absorption layer 2c are melted back by the InP layer 3c which fills the gap between the InGaAs small regions 2c and grows. Can be prevented.

[0025]

As described above, according to the semiconductor light receiving element and the method of manufacturing the same according to the present invention, a crystal layer serving as a light absorption layer of a small area of several μm is spread over the entire main surface of the substrate, Moreover, since the gap region of each of the light absorption layers is filled with the crystal having a wider forbidden band than the light absorption layer, the reflected light due to the background light becomes return light and adversely affects the light output characteristics of the semiconductor laser device. It is possible to eliminate the problem of giving and to improve the deterioration of the photodetection frequency characteristic due to the background light. Further, there is an effect that the manufacturing can be performed by a simple method.

[Brief description of drawings]

FIG. 1 is a sectional view showing a semiconductor light receiving element structure according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a transparent top view of the semiconductor light receiving element structure of the first embodiment.

FIG. 3 is a cross-sectional view showing the method for manufacturing the semiconductor light receiving element according to the first embodiment of the present invention.

FIG. 4 is a sectional view showing a method for manufacturing a semiconductor light receiving element according to a second embodiment of the invention.

FIG. 5 is a sectional view showing a method for manufacturing a semiconductor light receiving element according to a third embodiment of the invention.

FIG. 6 is a diagram showing a cross-sectional view of a semiconductor light receiving element structure of Conventional Example 1.

FIG. 7 is a sectional view of a semiconductor light receiving element of Conventional Example 2.

[Explanation of symbols]

1 n ⁺ InP substrate 2 InGaAs light absorption layer 2a, 2b, 2c InGaAs light absorption layer 3a, 3b, 3c InP window layer 4 SiN insulating film 5 cathode electrode 6 anode electrode 7 P ⁺ region 8 metal mask 9 InGaAs layer

Claims (9)

[Claims] 1. A semiconductor light-receiving element having a structure in which light-receiving regions of a plurality of semiconductor layers formed on a semiconductor substrate have pn junctions, and light is incident on the light-receiving regions in the semiconductor layers. In the semiconductor layer on the lower surface side of the junction, a plurality of small-area light absorbing layers are spread over the light receiving area on the main surface of the semiconductor substrate, and the gap area between the light absorbing layers is filled. , And a crystal layer having a forbidden band width wider than that of the light absorption layer is embedded and formed on the light absorption layer in the light receiving region and the crystal layer having a wide band gap. And a diffusion region forming a pn junction are formed. 2. The semiconductor light receiving element according to claim 1, wherein the plurality of small area light absorption layers are formed on the entire surface of the semiconductor substrate. 3. The semiconductor light receiving element according to claim 1, wherein the semiconductor substrate is an n-type InP substrate, the plurality of light absorption layers are n-type InGaAs layers, and the light absorption layers are embedded. The buried layer is n-type In
A semiconductor light receiving element, which is a P layer, and in which a p-type diffusion region is formed on the plurality of light absorption layers and the buried layer. 4. The method of manufacturing a semiconductor light receiving element according to claim 1, wherein a step of forming a crystal layer to be a light absorbing layer with a uniform thickness on the main surface of the semiconductor substrate, and the light absorbing layer are formed. A step of dividing and forming the light absorption layer of a plurality of small areas by etching the crystal layer using a mask pattern of a lattice pattern, and a gap region between the light absorption layers of the plurality of small areas by a liquid phase epitaxial method. Embedded in the crystal layer with a forbidden band width wider than that of the light absorption layer until a certain thickness is formed on the light absorption layer. And a step of forming a diffusion region for forming a pn junction therewith so as to reach a part of the underlying light absorption layer. 5. The manufacturing method according to claim 4, which manufactures the semiconductor light receiving element according to claim 3, wherein the semiconductor substrate is an n-type InP substrate, and the plurality of light absorption layers are n-type InGaAs layers. The buried layer filling the light absorption layer is n-type In
A method for manufacturing a semiconductor light-receiving element, which is a P layer, and in which a p-type diffusion region is formed on the plurality of light absorption layers and the buried layer. 6. The method for manufacturing a semiconductor light receiving element according to claim 4, wherein after the step of forming the light absorption layer with a uniform thickness on the main surface of the semiconductor substrate, the light absorption layer is formed into a plurality of small area light beams. Before the step of separately forming in the absorption layer, a step of forming a crystal having a uniform thickness which is not melted back by the wide bandgap crystal to be buried and grown thereafter is further included. Production method. 7. The method for manufacturing a semiconductor light receiving element according to claim 6, wherein the light absorption layer is an InGaAs layer, the buried crystal layer is an InP layer, and a crystal that is not melted back by the buried crystal is InGaAsP. A method for manufacturing a semiconductor light receiving element, comprising: 8. The method of manufacturing a semiconductor light receiving element according to claim 4, wherein after the step of dividing the light absorption layer into a plurality of light absorption layers having a small area, a crystal having a band gap wider than that of the light absorption layer is formed. Prior to the step of burying and growing the light-absorbing layer, the method further includes the step of forming a crystal that does not melt back the light-absorbing layer in a thin and uniform thickness on the surface and the side surface of the light-absorbing layer which has become the small region. And a method for manufacturing a semiconductor light receiving element. 9. The method for manufacturing a semiconductor light receiving element according to claim 8, wherein the light absorption layer is an InGaAs layer, the buried crystal layer is an InP layer, and the crystal that does not melt back the light absorption layer is InGaAsP. A method for manufacturing a semiconductor light receiving element, characterized in that