JP2001111094A - Infrared light receiving element and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an infrared light receiving element, which prevents drop of sensitivity, controls leakage current at the surface of quantum well layer and reduces dark current, and to provide a method of manufacturing the same element. SOLUTION: An infrared light receiving element utilizing a multiplex quantum well structure into a light-absorbing layer has a structure that a quantum well light-absorbing layer, clad layers formed at both ends of this quantum well light-absorbing layer and contact layers moreover formed at both ends of these clad layers are formed on a substrate for disordering the quantum well light- absorbing layer part, exposed to the light-receiving surface with diffusion of impurity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared light receiving device using a multiple quantum well structure as a light absorbing layer, and more particularly to a method for preventing a decrease in sensitivity, suppressing a leak current on the surface of a quantum well layer and reducing a dark current. And a method of manufacturing the same.

[0002]

2. Description of the Related Art In general, a light absorbing layer in an infrared wavelength region (3 μm or more) used in a conventional infrared light receiving element has HgCd.
A Te layer or the like is used. However, although there is a liquid phase growth method in the crystal growth method of the HgCdTe layer, techniques such as a vapor phase growth method are inexperienced, and even in the liquid phase growth method, when the Hg composition is small, it becomes difficult to control the HgCdTe composition. Would.

On the other hand, although the Bridgman method or the like exists as a HgCdTe bulk crystal growth method, composition control is difficult due to a difference in segregation coefficient between Hg and Cd, and a large single crystal having a uniform composition cannot be obtained.

Therefore, using a multiple quantum well structure, "about 3 to
An infrared light receiving element having sensitivity in a wavelength range of 10 μm ″ has been devised.

In such a conventional infrared light receiving element, electrons are photoexcited by incident light from the ground level in the quantum well to the continuous level of the barrier layer beyond the band discontinuity existing at the heterojunction interface. Then, the photoexcited carriers are extracted as an optical signal current by drifting due to an electric field generated due to a voltage applied to the element.

For example, as such a multiple quantum well structure, “AlGaAs / GaAs”, “AlGaAs / I
nGaAs "," InGaAsP / InP "and" Ga
It is manufactured by a combination such as InP / GaAs ".

However, in an infrared light receiving element using such a multiple quantum well structure as a light absorption layer, incident light is incident on the quantum well in parallel according to the selection rule of intraband transition due to light absorption in the quantum well. Light absorption is maximized,
When the incident light is perpendicularly incident on the quantum well, the light absorption becomes very small and the sensitivity cannot be obtained.

For this reason, an infrared light receiving element manufactured in an element shape that allows incident light to be incident obliquely on an epitaxial wafer having a quantum well structure has been considered. FIG. 8 is a sectional view showing the configuration of an example of such a conventional infrared light receiving element.

In FIG. 8, 1 is a substrate, 2 and 6 are contact layers, and 3 and 5 are light absorption layers having a multiple quantum well structure of Al.
In the case of GaAs / GaAs, a cladding layer such as a GaAs layer formed on both sides of the light absorbing layer, 4 is a quantum well light absorbing layer, 7a and 7b are insulating layers such as silicon nitride and silicon oxide, 8a and 8b is an electrode.

A contact layer 2 is formed on a substrate 1,
A cladding layer 3 is formed on the contact layer 2. A quantum well light absorption layer 4 is formed on the cladding layer 3, and a cladding layer 5 is formed on the quantum well light absorption layer 4.

On the cladding layer 5, a contact layer 6 is formed, on the contact layers 2 and 5, electrodes 8a and 8b are formed, and on the contact layers 2 and 5, the electrode 8a is formed. And 8b, the insulating layer 7a
And 7b are respectively formed.

Here, the operation of the conventional example shown in FIG. 8 will be described. Infrared light, which is incident light indicated by "IR01" in FIG. 8, is incident on a light receiving surface formed obliquely as indicated by "IA01" in FIG.

In the same manner as described above, electrons are optically excited by the incident light incident on the light receiving surface from the ground level in the quantum well to the continuous level of the barrier layer beyond the band discontinuity existing at the heterojunction interface, The photoexcited carriers drift due to an electric field generated due to the voltage applied to the device, and are taken out as an optical signal current.

In the structure shown in FIG. 8, light is incident not obliquely on the quantum well light absorbing layer 4 but obliquely. Therefore, compared with the case where incident light is incident on the quantum well light collecting layer 4 vertically. As a result, light absorption increases and sensitivity can be obtained.

As a result, by adopting an element shape that allows incident light to enter the epitaxial wafer having the quantum well structure obliquely, light absorption is increased and sensitivity can be obtained.

Here, the manufacturing method of the conventional example shown in FIG. 8 will be described with reference to FIG. 9 and FIGS. FIG. 9 is a flowchart for explaining a conventional manufacturing method, and FIGS.
FIG. 3 is a cross-sectional view showing the structure of the infrared light receiving element in each step. Also. The reference numerals shown in FIGS. 10 to 19 are the same as those in FIG.

In a step indicated by "S001" in FIG. 9, a contact layer 2 is formed on a substrate 1 by using an epitaxial growth method such as metal organic chemical vapor deposition (MOVPE) or molecular beam epitaxy (MBE). For example, "S" in FIG.
In the step indicated by "001", the structure is as shown in FIG.

In the step indicated by "S002" in FIG. 9, the cladding layer 3 is formed on the contact layer 2 by using the above-mentioned epitaxial growth method. For example, “S002” in FIG.
In the process shown in FIG. 11, the structure as shown in FIG. 11 is obtained.

In the step indicated by "S003" in FIG. 9, the quantum well light absorption layer 4 is formed on the cladding layer 3 by using the above-mentioned epitaxial growth method. For example, “S00” in FIG.
In the step indicated by 3 ", the structure is as shown in FIG.

In the step indicated by "S004" in FIG. 9, the quantum well light absorbing layer 4 is formed using the above-described epitaxial growth method.
A cladding layer 5 is formed thereon. For example, “S00” in FIG.
The structure shown in FIG. 13 is obtained in the step shown in FIG.

In the step indicated by "S005" in FIG. 9, a contact layer 6 is formed on the cladding layer 5 by using the above-mentioned epitaxial growth method. For example, “S005” in FIG.
In the process shown in FIG. 14, the structure as shown in FIG. 14 is obtained.

In order to separate the elements in the step indicated by "S006" in FIG. 9, the etching is performed up to the cladding layer 3 and the contact layer 2 is separated. For example, in the step indicated by "S006" in FIG. 9, the portion indicated by "ET01" in FIG. 15 is removed by etching as shown in FIG.

In the step indicated by "S007" in FIG. 9, an insulating layer 7a is formed on the contact layer 6, and an insulating layer 7b is formed on the substrate 1 and the contact layer 2, respectively. For example,
In the step indicated by "S007" in FIG. 9, the structure is as shown in FIG.

In the step indicated by "S008" in FIG. 9, the insulating layers 7a and 7b are partially removed to form the electrodes 8a and 8b, respectively. For example, “S008” in FIG.
In the process shown in FIG. 17, the structure as shown in FIG. 17 is obtained.

Finally, in the step indicated by "S009" in FIG. 9, the light receiving surface is formed by anisotropic etching to form a light receiving surface, and the element is cut by cleavage or dicing. Since the etching rate differs from the anisotropic etching depending on the crystal plane, etching is performed obliquely along the crystal plane.

For example, in the step indicated by "S009" in FIG. 9, the portion indicated by "ET11" in FIG. 18 is obliquely etched and removed as shown in FIG. And FIG.
By cutting the portion indicated by the middle “CP11” by cleavage or dicing, an infrared light receiving element having a structure as shown in FIG. 19 can be manufactured.

[0027]

However, in the conventional example shown in FIG. 8 and the like, a part of the quantum well light absorbing layer 4 is exposed on the light receiving surface indicated by "IA01" in FIG. There is a problem that the photoexcited carriers generated on the surface are reduced by the carrier recombination center and the sensitivity is lowered. Further, there is a problem that the surface leak current is generated as a dark current of the infrared light receiving element. Therefore, an object of the present invention is to realize an infrared light receiving element capable of preventing a decrease in sensitivity, suppressing a leak current on the surface of a quantum well layer and reducing a dark current, and a method for manufacturing the same.

[0028]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 of the present invention relates to an infrared light receiving element using a multiple quantum well structure for a light absorption layer.
A quantum well light absorption layer, cladding layers formed at both ends of the quantum well light absorption layer, and contact layers further formed at both ends of these cladding layers are formed on the substrate, and are exposed on the light receiving surface. Since the quantum well light absorbing layer is made disordered by impurity diffusion, the rate of reduction of photoexcited carriers due to carrier recombination centers is reduced, so that a decrease in sensitivity can be prevented.

According to a second aspect of the present invention, in the infrared light receiving element according to the first aspect, the quantum well light absorbing layer exposed on the light receiving surface is disordered by impurity diffusion and a p-type layer is formed. With this configuration, the leakage current on the surface of the quantum well layer is suppressed, and the dark current can be reduced.

According to a third aspect of the present invention, in the infrared light receiving element according to the first and second aspects, the light receiving surface is formed so that incident light can be obliquely incident on the quantum well light absorbing layer. Is formed, the light absorption becomes larger as compared with the case where the incident light is perpendicularly incident on the quantum well light collecting layer.

According to a fourth aspect of the present invention, there is provided a method of manufacturing an infrared light receiving element using a multiple quantum well structure for a light absorbing layer.
Forming a first contact layer, a first clad layer, a quantum well light absorbing layer, a second clad layer, and a second contact layer on a substrate in order by using an epitaxial growth method; A step of forming an insulating layer on the first and second contact layers; a step of forming a diffusion window for impurity diffusion on the insulating layer; and a step of performing impurity diffusion to expose the quantum well light absorbing layer. The step of disordering the portion and the step of forming the electrode by removing a part of the insulating layer respectively prevent a decrease in the sensitivity of the photoexcited carriers because the rate of reduction by the carrier recombination center is reduced. It becomes possible.

According to a fifth aspect of the present invention, there is provided a method of manufacturing an infrared light receiving element using a multiple quantum well structure for a light absorbing layer.
Forming a first contact layer, a first clad layer, a quantum well light absorbing layer, a second clad layer, and a second contact layer on a substrate in order by using an epitaxial growth method; A step of forming an insulating layer on the first and second contact layers; a step of forming a diffusion window for impurity diffusion on the insulating layer; and a step of performing impurity diffusion to expose the quantum well light absorbing layer. A step of forming a p-type layer together with disordering the portion, and a step of forming an electrode by removing a part of the insulating layer, thereby suppressing a leak current on the surface of the quantum well layer and reducing a dark current. Reduction becomes possible.

According to a sixth aspect of the present invention, there is provided a method of manufacturing an infrared light receiving element using a multiple quantum well structure for a light absorbing layer.
Forming a first contact layer, a first clad layer, a quantum well light absorbing layer, a second clad layer, and a second contact layer on a substrate in order by using an epitaxial growth method; A step of forming an insulating layer on the first and second contact layers; a step of forming a diffusion window for impurity diffusion on the insulating layer; and a step of performing impurity diffusion to expose the quantum well light absorbing layer. Forming a p-type layer while disordering the portion, forming an electrode by removing a part of the insulating layer, and obliquely incident light with respect to the quantum well light absorption layer by anisotropic etching. Forming a light receiving surface so that light can be incident on the quantum well light collection layer, whereby light absorption is increased as compared with the case where incident light is perpendicularly incident on the quantum well light collecting layer.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view showing the configuration of an embodiment of the infrared light receiving element according to the present invention. In FIG. 1, reference numerals 1 to 6, 8a and 8b denote the same reference numerals as in FIG. 8, 7c and 7d denote insulating layers, and 9a and 9b denote p-type layers.

A contact layer 2 is formed on a substrate 1,
A cladding layer 3 is formed on the contact layer 2. A quantum well light absorption layer 4 is formed on the cladding layer 3, and a cladding layer 5 is formed on the quantum well light absorption layer 4.

A contact layer 6 is formed on the cladding layer 5, and electrodes 8 a and 8 b are formed on the contact layers 2 and 6. Then, the p-type layers 9a and 9b are formed by p-type impurity diffusion or the like, and at the same time, the quantum well light absorbing layer 4 and the exposed portion of the end face have a window structure in which the quantum well structure is disordered by p-type impurity diffusion or the like. Become.

Further, insulating layers 7c and 7d are formed on the contact layers 2 and 6 except for the electrodes 8a and 8b or the p-type layers 9a and 9b.

Here, the operation of the conventional example shown in FIG. 1 will be described. Infrared light, which is incident light indicated by "IR11" in FIG. 1, is incident on a light receiving surface formed obliquely as indicated by "IA11" in FIG.

In the same manner as described above, electrons are optically excited by the incident light incident on the light receiving surface from the ground level in the quantum well to the continuous level of the barrier layer beyond the band discontinuity existing at the heterojunction interface, The photoexcited carriers drift due to an electric field generated due to the voltage applied to the device, and are taken out as an optical signal current.

In the structure shown in FIG. 1, as in the conventional example, light is incident not obliquely on the quantum well light absorbing layer 4 but obliquely, so that the incident light is perpendicularly incident on the quantum well light collecting layer 4. As compared with the case where the light is incident, light absorption is increased and sensitivity can be obtained.

Further, the window structure in which the quantum well structure formed by p-type impurity diffusion or the like is disordered and the p-type layer 9a
And 9b have an equivalent band gap larger than that of the conventional example, so that the surface leakage current is suppressed.

By forming the p-type layers 9a and 9b, a pn junction is formed between the p-type layers 9a and 9b, the cladding layers 3 and 5, and the quantum well light absorption layer 4, so that the surface leakage current is reduced. Is suppressed.

On the other hand, the exposed portions at both ends of the quantum well light absorbing layer 4 are disordered in the quantum well structure due to p-type impurity diffusion or the like. As a result, the rate of decrease becomes small, so that a decrease in sensitivity can be prevented.

As a result, the exposed portions at both ends of the quantum well light absorbing layer have a window structure in which the exposed portions are disordered by impurity diffusion or the like, so that the rate of reduction of the photoexcited carriers due to the carrier recombination center is reduced, thereby reducing the sensitivity. Can be prevented.

Further, the exposed portions at both ends of the quantum well light absorbing layer are disordered by impurity diffusion or the like and the p-type layer is formed, thereby suppressing a leak current on the surface of the quantum well layer and reducing a dark current. become.

Furthermore, by adopting an element shape that allows incident light to enter the quantum well light absorbing layer obliquely, light absorption can be reduced as compared with the case where incident light enters the quantum well light collecting layer perpendicularly. growing.

Here, the manufacturing method of the embodiment shown in FIG. 1 will be described with reference to FIG. 2 and FIGS. FIG. 2 is a flow chart for explaining the manufacturing method of the embodiment, and FIGS. 3 to 7 are sectional views showing the structure of the infrared light receiving element in each step. Also. 3 to 7 are denoted by the same reference numerals as in FIG.

The description of the same steps as those of the conventional manufacturing method shown in FIG. 9 will be omitted. Therefore, the description regarding “S101” to “S107” in FIG.
The description is omitted because it is the same as the middle “S001” to “S007”. However, the insulating layers 7a and 7b are to be read as the insulating layers 7c and 7d, respectively.

In step S108 shown in FIG. 2, a diffusion window for impurity diffusion is formed on insulating layer 7c formed in the previous step. For example, in the process shown in "S108" in FIG. 2, "DW11" and "DW12" in FIG. 3 are formed on the insulating layer 7c.
A diffusion window as shown in FIG.

Impurities are diffused from the diffusion window formed in the step shown in "S109" in FIG.
Are disordered to form p-type layers 9a and 9b. For example, in the step indicated by "S109" in FIG. 2, the structure becomes as shown in FIG. 4, and the p-type layers 9a and 9b are formed.

Further, in the step indicated by "S110" in FIG. 2, the insulating layers 7c and 7d are partially removed to form the electrodes 8a and 8b, respectively. For example, “S110” in FIG.
In the process shown in FIG. 5, the structure as shown in FIG. 5 is obtained.

Finally, in the step indicated by "S111" in FIG. 2, the light receiving surface is formed by oblique etching by anisotropic etching, and the element is cut by cleavage or dicing.

For example, in the step indicated by "S111" in FIG. 2, the portion indicated by "ET21" in FIG. 6 is obliquely etched and removed as shown in FIG. And "C" in FIG.
By cutting the portion indicated by P21 ″ by cleavage or dicing, an infrared light receiving element having a structure as shown in FIG. 7 can be manufactured.

In the embodiment shown in FIG. 1, the light receiving surface is formed so that incident light can be obliquely incident on the quantum well light absorbing layer. A disordered window structure may be formed by impurity diffusion or the like.

In other words, it is also possible to form a window structure in which the quantum well light absorption layer exposed on the light receiving surface is disordered due to impurity diffusion or the like without forming the light receiving surface obliquely by performing anisotropic etching. .

Further, in the embodiment shown in FIG. 1, the light receiving surface is formed so that incident light can be obliquely incident on the quantum well light absorbing layer. What is necessary is just to make the layer disorder by impurity diffusion or the like and to form a p-type layer.

In other words, the quantum well light absorption layer exposed on the light receiving surface is not disordered by impurity diffusion or the like without performing the anisotropic etching to form the light receiving surface obliquely, and the p-type region is formed.
The formation of the shape layer may be sufficient.

Although the insulating layers 7c and 7d are necessary in the manufacturing process, the resulting infrared light receiving element is not an essential component because there is no need to particularly insulate it from other layers.

[0059]

As is apparent from the above description,
According to the present invention, the following effects can be obtained. According to the first and fourth aspects of the present invention, the exposed portions at both ends of the quantum well light absorption layer have a window structure in which the exposed portions are disordered by impurity diffusion or the like, whereby the rate of reduction of photoexcited carriers due to carrier surface recombination centers is reduced. Becomes smaller, so that a decrease in sensitivity can be prevented.

According to the second and fifth aspects of the present invention, the exposed portions at both ends of the quantum well light absorbing layer are disordered by impurity diffusion and the like, and the p-type layer is formed. And the dark current can be reduced.

According to the third and sixth aspects of the present invention, by adopting an element shape that allows incident light to enter the quantum well light absorbing layer obliquely, the incident light enters the quantum well light collecting layer. Has a greater light absorption than when vertically incident.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the configuration of an embodiment of an infrared light receiving element according to the present invention.

FIG. 2 is a flowchart illustrating a manufacturing method according to an embodiment.

FIG. 3 is a cross-sectional view showing a structure of an infrared light receiving element in each step.

FIG. 4 is a cross-sectional view showing a structure of an infrared light receiving element in each step.

FIG. 5 is a cross-sectional view showing the structure of the infrared light receiving element in each step.

FIG. 6 is a cross-sectional view showing the structure of the infrared light receiving element in each step.

FIG. 7 is a cross-sectional view showing the structure of the infrared light receiving element in each step.

FIG. 8 is a sectional view showing a configuration of an example of a conventional infrared light receiving element.

FIG. 9 is a flowchart illustrating a manufacturing method of a conventional example.

FIG. 10 is a cross-sectional view showing the structure of the infrared light receiving element in each step.

FIG. 11 is a cross-sectional view showing the structure of the infrared light receiving element in each step.

FIG. 12 is a cross-sectional view showing the structure of the infrared light receiving element in each step.

FIG. 13 is a cross-sectional view showing the structure of the infrared light receiving element in each step.

FIG. 14 is a cross-sectional view showing the structure of the infrared light receiving element in each step.

FIG. 15 is a cross-sectional view showing the structure of the infrared light receiving element in each step.

FIG. 16 is a cross-sectional view showing the structure of the infrared light receiving element in each step.

FIG. 17 is a cross-sectional view showing the structure of the infrared light receiving element in each step.

FIG. 18 is a cross-sectional view showing the structure of the infrared light receiving element in each step.

FIG. 19 is a cross-sectional view showing the structure of the infrared light receiving element in each step.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2, 6 Contact layer 3, 5 Cladding layer 4 Quantum well light absorption layer 7a, 7b, 7c, 7d Insulating layer 8a, 8b Electrode 9a, 9b P-type layer

Claims (6)

[Claims] An infrared light receiving device using a multiple quantum well structure as a light absorption layer, comprising: a quantum well light absorption layer; cladding layers formed at both ends of the quantum well light absorption layer; An infrared light receiving element, wherein contact layers further formed at both ends are formed on a substrate, and the quantum well light absorbing layer exposed on the light receiving surface is disordered by impurity diffusion. 2. The infrared light receiving element according to claim 1, wherein the quantum well light absorbing layer exposed on the light receiving surface is disordered by impurity diffusion and a p-type layer is formed. 3. The infrared light receiving element according to claim 1, wherein said light receiving surface is formed so that incident light can be obliquely incident on said quantum well light absorbing layer. 4. A method of manufacturing an infrared light receiving device using a multiple quantum well structure as a light absorption layer, wherein a first contact layer, a first cladding layer, and a quantum well light absorption layer are formed on a substrate by epitaxial growth. Forming a second cladding layer and a second contact layer sequentially; separating the elements; forming an insulating layer on the first and second contact layers; A step of forming a diffusion window for impurity diffusion thereon, a step of performing impurity diffusion to disorder the exposed portion of the quantum well light absorbing layer, and a step of forming electrodes by removing a part of the insulating layer. A method for manufacturing an infrared light receiving element. 5. A method for manufacturing an infrared light receiving device using a multiple quantum well structure as a light absorption layer, comprising: a first contact layer, a first cladding layer, and a quantum well light absorption layer on a substrate by using an epitaxial growth method. Forming a second cladding layer and a second contact layer sequentially; separating the elements; forming an insulating layer on the first and second contact layers; A step of forming a diffusion window for impurity diffusion thereon; a step of forming a p-type layer while disordering an exposed portion of the quantum well light absorption layer by performing impurity diffusion; and removing a part of the insulating layer to form an electrode. And a step of forming each of the above. 6. A method of manufacturing an infrared light receiving device using a multiple quantum well structure as a light absorption layer, comprising: a first contact layer, a first cladding layer, and a quantum well light absorption layer on a substrate by using an epitaxial growth method. Forming a second cladding layer and a second contact layer sequentially; separating the elements; forming an insulating layer on the first and second contact layers; A step of forming a diffusion window for impurity diffusion thereon; a step of forming a p-type layer while disordering an exposed portion of the quantum well light absorption layer by performing impurity diffusion; and removing a part of the insulating layer to form an electrode. And a step of forming a light receiving surface by anisotropic etching so that incident light can be obliquely incident on the quantum well light absorbing layer. Method.