JP2006286825A - Photoelectric converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric converter capable of selectively receiving necessary visible light without increasing the number of components. <P>SOLUTION: The photoelectric converter 10 for converting a green optical signal into an electric signal includes a light receiving layer 52 of In<SB>0.4</SB>Ga<SB>0.6</SB>N, a pair of interdigital electrodes 72 and 74 with potential difference and in electric contact with the surface of the layer 52, and a first filter 32 of GaN and a second filter 34 of In<SB>0.2</SB>Ga<SB>0.8</SB>N provided toward an incident surface from the light receiving layer 52 and having a wider band gap than that of the layer 52. The filter layers 32 and 34 absorb visible light with a shorter wavelength than that of the visible light absorbed by the layer 52. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a photoelectric conversion device that converts light energy into electrical energy. In particular, the present invention relates to a photoelectric conversion device that selects light energy of light having a required wavelength from incident light including light having a plurality of wavelengths and converts the light energy into electric energy.
In the following specification, an example of a photoelectric conversion device that is used in combination with a plastic optical fiber (hereinafter referred to as POF) and used to convert an optical signal transmitted by the POF into an electrical signal will be taken up. explain. However, the technology disclosed in this specification is not limited to the application. The technical element disclosed in the present specification can be widely used in a photoelectric conversion device that converts light energy into electric energy.

There are many scenes where an optical communication system is constructed over a relatively short distance and a large amount of information is to be transmitted and received. In such a case, researches have been made to construct an optical communication system at low cost using POF.
In an optical communication system using POF or the like, it is preferable to use a visible light region with a small transmission loss. For this reason, in an optical communication system using POF, research on a photoelectric conversion device using a III-V group compound semiconductor that absorbs visible light in a light receiving layer is underway. For example, when the ultraviolet light region and the visible light region are used, the general formula is Al _X Ga _Y In _1-XY N (where 0 ≦ X ≦ 1, 0 ≦ Y ≦ 1, 0 ≦ 1−XY). A group III-V compound semiconductor represented by ≦ 1) is often used.

In such an optical communication system, a single optical fiber is used to transmit an optical signal including visible light of multiple wavelengths in one direction, or a single optical fiber is used to display multiple wavelengths of visible light. Research is being conducted on systems that transmit and receive optical signals including light in both directions. Such an optical communication system is called a multiple communication system. Non-Patent Document 1 describes a multiplex communication system using POF.
In a multiplex communication system using the visible light region, a technique for selectively receiving visible light having a necessary wavelength from an optical signal transmitted through an optical fiber is required. Generally, a colored package is provided in the photoelectric conversion device to block unnecessary visible light, or a module having an optical filter for wavelength demultiplexing is provided on the main line of the optical fiber, and only a necessary wavelength is provided. A method of guiding the light to a photoelectric conversion device is used.
However, regardless of which method is employed, it is necessary to provide separate components for the photoelectric conversion device, and there are many problems in terms of cost increase and miniaturization due to an increase in the number of components.

As one technique for coping with such a problem, Patent Document 1 proposes a technique in which a plurality of semiconductor light absorption layers having light absorption in different wavelength regions are provided in a semiconductor stack of a photoelectric conversion device. If this technique is used, it becomes possible to selectively receive light having a required wavelength without providing a separate component.
Yoshihiro Someno, Kimihiro Kikuchi, “POF LAN”, O plus E, published on June 5, 1999, Vol. 21, No. 6, p. 679-684 JP2003-142721

However, the semiconductor light absorption layer provided in the photoelectric conversion device of Patent Document 1 has a longitudinal conduction type structure using a PIN structure. In addition to the semiconductor light absorption layer, the PIN structure includes an n-type semiconductor layer and a p-type semiconductor layer in contact with the upper and lower surfaces of the semiconductor light absorption layer. For this reason, since the semiconductor light absorption layer using the PIN structure requires a plurality of semiconductor layers, the number of steps required for manufacturing increases.
An object of the present invention is to provide a photoelectric conversion device that can selectively receive light having a necessary wavelength without increasing the number of components and that has a simple structure.

One feature of the present invention is that a filter layer with an adjusted band gap is formed in a semiconductor stack of a photoelectric conversion device. Another feature of the present invention is that a pair of electrodes having a potential difference is formed on the surface of the light receiving layer.
Light of unnecessary wavelengths is blocked by a filter layer built in the photoelectric conversion device. Since the filter layer is built into the semiconductor stack, there is no need to provide a separate component for blocking unwanted wavelengths. Therefore, the photoelectric conversion device of the present invention can selectively receive visible light having a necessary wavelength without increasing the number of components.
Further, electrons and holes generated in the light receiving layer move in the horizontal direction in the surface of the light receiving layer and are taken out from the pair of electrodes. Therefore, there is no need to form an n-type semiconductor layer and a p-type semiconductor layer on the upper and lower surfaces of the light receiving layer. The structure of the photoelectric conversion device of the present invention is simplified, and the number of steps required for manufacturing is small.
As will be described later, the filter layer not only blocks light of unnecessary wavelengths, but also extracts electrons and holes generated by receiving light of unnecessary wavelengths with the filter layer as electric energy. it can. That is, the filter layer is a filter that blocks light having an unnecessary wavelength when viewed from the light receiving layer, but is also a light receiving layer that receives light having an unnecessary wavelength. If the light of the wavelength received by the filter layer is a significant optical signal, it is also a light receiving layer that receives the significant optical signal. By adopting a structure in which the filter layer is also a light receiving layer, light energy of light having a plurality of wavelengths can be converted into electric energy by one photoelectric conversion device. The structure in which the filter layer is also the light receiving layer can be laminated in multiple layers.

The present invention can be embodied in a photoelectric conversion device that converts light energy into electrical energy. The photoelectric conversion device of the present invention is provided on the light-receiving layer side of the light-receiving layer of the III-V compound semiconductor, a pair of electrodes having a potential difference and being in electrical contact with the surface of the light-receiving layer. And a III-V group compound semiconductor filter layer having a wider band gap than the light receiving layer. The filter layer absorbs light having a shorter wavelength than the light absorbed by the light receiving layer. The filter layer may include a second filter layer that absorbs light of other wavelengths as necessary.
Of incident light including light having a plurality of wavelengths incident on the incident surface, light having a short wavelength is absorbed by the filter layer. Of the incident light including light having a plurality of wavelengths incident on the incident surface, light having a long wavelength passes through the filter layer and is absorbed by the light receiving layer. Since light having a short wavelength is removed by the filter layer, the proportion of light having a long wavelength is increased in the light absorbed by the light receiving layer. A photoelectric conversion device having an improved S / N ratio can be obtained. Further, electrons and holes generated in the light receiving layer move in the horizontal direction in the surface of the light receiving layer and are taken out from the pair of electrodes.
In the photoelectric conversion device of the present invention, a necessary wavelength can be selectively incident on the light receiving layer by providing a filter layer in the semiconductor stack of the photoelectric conversion device. The above effect can be obtained without providing other components outside the photoelectric conversion device. The above effects can be obtained without substantially increasing the size of the photoelectric conversion device. Furthermore, since a charge can be taken out using a pair of electrodes provided on the surface of the light receiving layer, a plurality of semiconductor layers are not required unlike the PIN type. The structure of the photoelectric conversion device is simplified. Since the number of steps required for manufacturing is small, the manufacturing cost can be reduced.

The band width of the light receiving layer is adjusted so as to absorb the light energy of visible light, and the filter layer has a band gap so as to absorb visible light having a shorter wavelength than the visible light absorbed by the light receiving layer. It is preferable that the width is adjusted.
A photoelectric conversion device that separates visible light and visible light having different wavelengths can be obtained.

The filter layer may be formed between a pair of electrodes on the surface of the light receiving layer. In this case, incident light enters from above the surface where the pair of electrodes are exposed.
When the above structure is employed, a photoelectric conversion device including a pair of electrodes on the surface of the light receiving layer and including a filter layer can be obtained.

It is preferable that a barrier layer having a wider band gap than the light receiving layer and the filter layer is formed between the light receiving layer and the filter layer.
By providing the barrier layer, an energy barrier is formed between the light receiving layer and the filter layer. This energy barrier prevents electrons and holes generated in the filter layer from flowing into the light receiving layer. The electron / hole generated in the filter layer is prevented from being superimposed on the electron / hole generated in the light receiving layer. A photoelectric conversion device having a significantly improved S / N ratio can be obtained.

The III-V group compound semiconductor is preferably Al _X Ga _Y In _1-XY N (where 0 ≦ X ≦ 1, 0 ≦ Y ≦ 1, 0 ≦ 1-X−Y ≦ 1).
When the light receiving layer and the filter layer are formed using the above materials, the visible light region can be received from the ultraviolet light region. The photoelectric conversion device of the present invention can be suitably used for an optical communication system using POF or the like.

A pair of electrodes having a potential difference is preferably in electrical contact with the surface of the filter layer.
Electrons and holes generated in the filter layer flow into the pair of electrodes based on the potential difference between the pair of electrodes, and are converted into electrical energy. A structure in which the filter layer also functions as a light receiving layer is obtained. Accordingly, electrical energy corresponding to light of different wavelengths can be obtained in each of the light receiving layer and the filter layer. Light of a plurality of wavelengths can be received by one photoelectric conversion device.

  In the photoelectric conversion device of the present invention, a plurality of semiconductor layers having band gaps adjusted appropriately with respect to light of a plurality of wavelengths are provided in the semiconductor stack of the photoelectric conversion device. This makes it possible to selectively receive necessary light from incident light including light of a plurality of wavelengths. This photoelectric conversion device enables the discrimination of visible light having a plurality of wavelengths without substantially providing other components. Furthermore, the electrons and holes generated in the light receiving layer are taken out from a pair of electrodes provided on the surface of the light receiving layer. The structure is simplified and the structure is easy to manufacture.

The main features of the examples are listed.
(First Form) It is preferable that a pair of electrodes having a potential difference is in electrical contact with the surface of the light receiving layer. Thereby, it is possible to obtain a lateral conduction type structure in which electrons and holes generated by incident light flow in a lateral direction between a pair of electrodes. The generated electrons and holes can be allowed to flow into the pair of electrodes without being interfered by the filter layer.
(2nd form) It is preferable to set it as the structure provided with the several filter layer. Excessive generation of electrons and holes can be prevented locally.
(Third Embodiment) The III-V group compound semiconductor is represented by Al _X Ga _Y In _1-XY N (where 0 ≦ X ≦ 1, 0 ≦ Y ≦ 1, 0 ≦ 1-X−Y ≦ 1). It is preferable to use a binary, ternary or quaternary semiconductor material. Some of these group III elements may be replaced with boron (B) or thallium (Tl). Further, part of nitrogen (N) may be replaced with phosphorus (P), arsenic (As), antimony (Sb), or bismuth (Bi). Furthermore, Si, Ge, Se, Te, C, etc. may be added to these semiconductor materials as n-type impurities, and Be, Ca, Sr, Ba, etc. may be added as p-type impurities.

(First embodiment)
In FIG. 1, the principal part sectional drawing of the photoelectric conversion apparatus 10 is shown. FIG. 2 shows a plan view of the photoelectric conversion device 10. A vertical cross section corresponding to line I-I in FIG. 2 corresponds to a cross-sectional view of the main part in FIG.
As indicated by the arrows in FIG. 1, the photoelectric conversion device 10 receives incident light from below. Incident light extends to the visible light region including the ultraviolet light region to the green light region.
The photoelectric conversion device 10 includes a semiconductor stack of a substrate 22, a buffer layer 24, a first filter layer 32, a second filter layer 34, a barrier layer 42, and a light receiving layer 52 in order from the incident surface side. The first filter layer 32 and the second filter layer 34 are provided on the incident surface side with respect to the light receiving layer 52. The barrier layer 42 is provided between the light receiving layer 52 and the second filter layer 34. A pair of comb electrodes 72 and 74 are formed in electrical contact with the surface of the light receiving layer 52.

  The substrate 22 is formed using sapphire. The material of the substrate 22 may be any material that transmits visible light received by the light-receiving layer 52. Instead of sapphire, spinel, gallium phosphide, gallium arsenide, silicon carbide, gallium oxide, zinc oxide, magnesium oxide Further, manganese oxide, or a III-V group compound semiconductor similar to the light receiving layer 52 and the filter layers 32 and 34 can also be used.

  The buffer layer 24 is formed using aluminum nitride (AlN) having a thickness of about 0.05 μm. The buffer layer 24 is formed in order to reduce crystal defects in the semiconductor stack formed on the substrate 22. As the material of the buffer layer 24, a material having a lattice constant close to the lattice constant of the crystal laminated on the buffer layer 24 is employed.

  The first filter layer 32 is formed using gallium nitride (GaN) having a thickness of about 4.0 μm. As the material of the first filter layer 32, a material having a band gap wider than the band gaps of the light receiving layer 52 and the second filter layer 34 is employed. Furthermore, the band gap of the first filter layer 32 is adjusted to a size that can absorb the light energy of ultraviolet light.

The second filter layer 34 is formed using gallium indium nitride (In _0.2 Ga _0.8 N) having a thickness of about 0.2 μm. The material of the second filter layer 34 is a material having a band gap that is wider than the band gap of the light receiving layer 52 and narrower than the band gap of the first filter layer 32. Further, the band gap of the second filter layer 34 is adjusted to a size capable of absorbing the optical energy of visible light having a shorter wavelength than the visible light received by the light receiving layer 52.

  The barrier layer 42 is formed using gallium nitride (GaN) having a thickness of about 0.015 μm. As the material of the barrier layer 42, a material having a wider band gap than that of the light receiving layer 52 and the second filter layer 34 is employed.

The light receiving layer 52 is formed using gallium nitride indium (In _0.4 Ga _0.6 N) having a thickness of about 0.020 μm. The light receiving layer 52 is made of a material having a narrower band gap than the band gaps of the first filter layer 32 and the second filter layer 34. Further, the band gap of the light receiving layer 52 is adjusted to a size capable of absorbing the wavelength of a visible light optical signal (which is light energy) to be received.

As shown in FIG. 2, a pair of comb electrodes 72 and 74 are formed in electrical contact with the surface of the light receiving layer 52. A constant potential is applied to the comb electrode 72 and the comb electrode 74, and a potential difference is formed between them. The pair of comb electrodes 72 and 74 are made of platinum (Pt) and have a thickness of 0.05 μm.
The distance between the pair of comb electrodes 72 and 74 is formed with a distance of about several μm so that electrons and holes excited by incident light flow between the pair of comb electrodes 72 and 74. The shapes of the comb electrode 72 and the comb electrode 74 may be symmetric or may not be symmetric.

In FIG. 3, the band diagram of the semiconductor lamination of the photoelectric conversion apparatus 10 is shown. The reference numerals in the figure coincide with the reference numerals of each layer. The light receiving layer 52 of the photoelectric conversion device 10 uses green light as a sensitivity wavelength region, and the photoelectric conversion device 10 converts an optical signal corresponding to the green light into an electric signal (in this embodiment, a current signal).
As shown in FIG. 3, the photoelectric conversion device 10 is provided with a first filter layer 32 having a wide energy band on the incident surface side. The first filter layer 32 absorbs ultraviolet light having a short wavelength among incident light including the ultraviolet light region to the green light region. Blue light and green light having a long wavelength pass through the first filter layer 32 and enter the second filter layer 34.
The second filter layer 34 absorbs blue light having a short wavelength and transmits green light having a long wavelength. Therefore, only the green light reaches the light receiving layer 52 among the wavelength components of the incident light.
The light receiving layer 52 absorbs green light and generates electrons and holes. The generated electrons / holes move laterally in the plane of the light receiving layer 52 and flow into the pair of comb electrodes 72 and 74. Therefore, when the photoelectric conversion device 10 is used, only green light can be incident on the light receiving layer 52 from incident light including visible light having a plurality of wavelengths. The photoelectric conversion device 10 can selectively extract an optical signal corresponding to green light and obtain an electrical signal (current signal in this embodiment) corresponding to the optical signal. For this reason, in the photoelectric conversion device 10, disturbance due to optical signals of other wavelengths, external light, and the like are remarkably suppressed, and the S / N ratio is high.

The photoelectric conversion device 10 has the following other features.
(1) The barrier layer 42 forms an energy barrier between the second filter layer 34 and the light receiving layer 52. The barrier layer 42 prevents electrons and holes generated by absorbing ultraviolet light and blue light in the first filter layer 32 and the second filter layer 34 from flowing into the light receiving layer 52. In particular, when operating at a high temperature, thermal charge is likely to move between the first filter layer 32 and the second filter layer 34 and the light receiving layer 52. In such a case, the barrier layer 42 is used. Is extremely effective. For this reason, the photoelectric conversion device 10 can flow only the electrons and holes generated by the green light into the pair of comb electrodes 72 and 74. The electrons / holes generated in the first filter layer 32 and the second filter layer 34 are prevented from being superimposed on the electrons / holes flowing into the pair of comb-tooth electrodes 72, 74. The S / N ratio is significantly improved.
Even if the barrier layer 42 is not formed, if the thickness of the second filter layer 34 is increased, electrons and holes generated in the first filter layer 32 and the second filter layer 34 flow into the light receiving layer 52. This can be prevented. However, when the thickness of the second filter layer 34 is increased, there is a problem that the crystal defect density also increases. Therefore, it can be said that the thickness of the second filter layer 34 can be reduced by providing the barrier layer 52. By providing the barrier layer 52, a photoelectric conversion device with a reduced crystal defect density can be obtained.
(2) The photoelectric conversion device 10 includes a plurality of filter layers (first filter layer 32 and second filter layer 34), and absorbs ultraviolet light and blue light separately. For this reason, it is prevented that excessive electrons and holes are locally generated, and the durability of the photoelectric conversion device 10 is improved. Note that, as necessary, the structure of only the first filter layer 32 or the structure of only the second filter layer 34 may be used.
(3) The photoelectric conversion device 10 has a structure (referred to as a lateral conduction type) in which electrons / holes generated by incident light flow in a lateral direction between a pair of comb electrodes 72 and 74. Conventionally known longitudinally conductive PIN photodiodes need to be provided with an n-type semiconductor layer and a p-type semiconductor layer in contact with the upper and lower surfaces of the light-receiving layer, resulting in a complicated structure. Furthermore, it is necessary to form electrodes for the n-type semiconductor layer and the p-type semiconductor layer, respectively. The electrode in contact with the n-type semiconductor layer and the electrode in contact with the p-type semiconductor layer are not located in the same plane and are offset in the thickness direction. For this reason, the electrode in contact with the n-type semiconductor layer and the electrode in contact with the p-type semiconductor layer each require a dedicated manufacturing process. For this reason, the structure of the photoelectric conversion device using the PIN structure is complicated, the number of steps required for manufacturing increases, and the yield is poor.
On the other hand, the photoelectric conversion device 10 of the present embodiment is a lateral conduction type in which a pair of comb electrodes 72 and 74 are provided on the surface of the light receiving layer 52. For this reason, the light receiving layer 52 can be constituted by one semiconductor layer, and the structure is simplified. Furthermore, since the pair of comb electrodes 72 and 74 are located in the same plane, they can be produced in the same manufacturing process.
(4) The photoelectric conversion device 10 can use the back surface side of the substrate 22 as the incident surface. For this reason, the surface on which the comb electrodes 72 and 74 are formed can be mounted in contact with the circuit board. Flip chip mounting is possible in which the electrodes are directly bonded to the lead frame or the conductor pattern of the printed circuit board. Therefore, it is possible to prevent a loss from being picked up by noise at the wire bonding portion or the like, and to reduce crosstalk and noise. In addition, since the photoelectric conversion device 10 can be mounted on the circuit board with the back surface of the substrate 22 serving as the incident surface facing up, it is easy to mount an optical fiber or an optical waveguide that guides light to the photoelectric conversion device 10. Furthermore, an optical fiber or an optical waveguide can be directly bonded to the back surface of the substrate 22, and the loss of light leaking from the gap between the two can be greatly reduced.
(5) An n-type impurity may be added to the light receiving layer 52 as necessary. When an impurity is added, the lifetime of the charge (lifetime) can be controlled. For example, when there is a response delay due to an electric field having a long lifetime with respect to a change in the intensity of incident light, the lifetime of charges can be shortened by adding impurities. For this reason, a photoelectric conversion device having high-speed response characteristics can be obtained.

(Method for manufacturing photoelectric conversion device 10)
Next, the manufacturing method of the photoelectric conversion apparatus 10 is demonstrated using FIG.
As shown in FIG. 4A, a substrate 22 made of sapphire is prepared. The surface a is selected as the surface of the substrate 22, and the surface is cleaned by organic cleaning and heat treatment.
First, while maintaining the temperature of the substrate 22 at 1100 ° C., hydrogen gas is supplied at a flow rate of 2 liters / minute, and the surface of the substrate 22 is vapor-phase etched.
Next, as shown in FIG. 4B, the temperature of the substrate 22 is lowered to 400 ° C., and the buffer layer 24 is formed on the substrate 22 by using the MOCVD method. At this time, hydrogen gas is supplied at 20 liters / minute, trimethylaluminum (TMAl) is supplied at 1.8 × 10 ⁻⁵ mol / minute as an aluminum raw material, and ammonia gas (NH ₃ ) is supplied at 10 liter / minute as a nitrogen raw material. It is preferable to supply in minutes.

Next, the temperature of the substrate 22 is maintained at 1150 ° C., and the first filter layer 32 is formed on the buffer layer 22 using the MOCVD method. At this time, trimethylgallium (TMG) can be suitably used as the gallium raw material, and ammonia gas (NH ₃ ) can be suitably used as the nitrogen raw material.
Next, the temperature of the substrate 22 is maintained at 850 ° C., and the second filter layer 34 is formed on the first filter layer 32 using the MOCVD method. At this time, hydrogen gas or nitrogen gas is supplied at 10 liters / minute, trimethylgallium (TMG) is supplied at 1.0 × 10 ⁻⁴ mol / minute as a gallium raw material, and ammonia gas (NH ₃ ) is supplied as a nitrogen raw material. It is preferable to supply at 10 liters / minute and to supply trimethylindium (TMI) at 0.2 × 10 ⁻⁴ mol / minute as an indium raw material.
Next, the barrier layer 42 is formed on the second filter layer 34 using the MOCVD method while maintaining the temperature of the substrate 22 at 850 ° C. At this time, hydrogen gas or nitrogen gas is supplied at a rate of 20 liters / minute, trimethylgallium (TMG) is supplied as a gallium source at 1.5 × 10 ⁻⁴ mol / minute, and ammonia gas (NH ₃ ) is supplied as a nitrogen source. It is preferable to supply at 10 liters / minute.
Next, the light receiving layer 52 is formed on the barrier layer 42 using the MOCVD method while keeping the temperature of the substrate 22 at 730 ° C. At this time, hydrogen gas or nitrogen gas is supplied at 20 liters / minute, trimethylgallium (TMG) is supplied at 1.0 × 10 ⁻⁴ mol / minute as a gallium raw material, and ammonia gas (NH ₃ ) is supplied as a nitrogen raw material. It is preferable to supply at 10 liters / minute and to supply trimethylindium (TMI) as an indium raw material at 0.5 × 10 ⁻⁴ mol / minute.
Finally, a pair of comb electrodes 72 and 74 are formed on the light receiving layer 52 by using a photolithography technique and an etching technique. The pair of comb electrodes 72 and 74 are simultaneously formed using the same manufacturing process.
The photoelectric conversion device 10 can be obtained through these steps.

(Second embodiment)
Next, the photoelectric conversion apparatus 100 of 2nd Example is demonstrated. However, components that are substantially the same as those in the first embodiment are denoted by the same reference numerals, and descriptions thereof may be omitted.
FIG. 5 shows a cross-sectional view of the main part of the photoelectric conversion device 100. FIG. 6 shows a plan view of the photoelectric conversion device 100. A vertical cross section corresponding to line VV in FIG. 6 corresponds to a cross-sectional view of the main part in FIG.
As indicated by an arrow in FIG. 5, the photoelectric conversion device 100 receives incident light from above. Incident light extends to the visible light region including the blue light region to the green light region.
The photoelectric conversion device 100 includes a semiconductor stack of a substrate 22, a buffer layer 24, a base layer 62, a light receiving layer 52, and a third filter layer 36 in order from the opposite side to the incident surface. The third filter layer 36 is provided on the incident surface side with respect to the light receiving layer 52. The third filter layer 36 has a comb-like opening. Reference numeral 36a denotes an opening boundary. A pair of comb electrodes 72 and 74 are formed in electrical contact with the surface of the light receiving layer 52. The comb electrodes 72 and 74 are formed in comb-shaped openings of the third filter layer 36. The third filter layer 36 is formed between the pair of comb electrodes 72 and 74 on the surface of the light receiving layer 52. It can be said that the third filter layer 36 is formed so as to cover a portion of the surface of the light receiving layer 52 other than the pair of comb-tooth electrodes 72 and 74.

The substrate 22 is formed using sapphire.
The buffer layer 24 is formed using aluminum nitride (AlN) having a thickness of about 0.05 μm.
The underlayer 62 is formed using gallium nitride (GaN) having a thickness of about 4.0 μm. The underlayer 62 is provided to alleviate the lattice mismatch between the buffer layer 24 and the light receiving layer 52.

The light receiving layer 52 is formed using gallium nitride indium (In _0.4 Ga _0.6 N) having a thickness of about 0.020 μm. As the material of the light receiving layer 52, a material having a band gap narrower than that of the third filter layer 36 is employed. Further, the band gap of the light receiving layer 52 is adjusted to a size capable of absorbing the wavelength of a visible light optical signal (which is light energy) to be received.

The third filter layer 36 is formed using gallium nitride indium (In _0.2 Ga _0.8 N) having a thickness of about 0.2 μm. As the material of the third filter layer 36, a material wider than the band gap of the light receiving layer 52 is employed. Further, the band gap of the third filter layer 36 is adjusted to a size capable of absorbing the optical energy of visible light having a shorter wavelength than the visible light received by the light receiving layer 52.

As shown in FIG. 6, a pair of comb electrodes 72 and 74 are formed on the surface of the light receiving layer 52. A constant potential is applied to the comb electrode 72 and the comb electrode 74, and a potential difference is formed between them. The pair of comb electrodes 72 and 74 are made of nickel (Ni) and have a thickness of 0.05 μm.
The pair of comb electrodes 72 and 74 may employ either a conductive material that is transparent to visible light or an opaque conductive material. In the case of a transparent material, more visible light can be incident on the light receiving layer 52. In the case of an opaque material, since visible light cannot reach the light receiving layer 52 unless it passes through the third filter layer 36, photoelectric conversion with a high S / N ratio is possible.

Incident light entering the photoelectric conversion device 100 is visible light including a blue light region to a green light region. The third filter layer 36 absorbs blue light having a short wavelength and transmits green light having a long wavelength. Therefore, only the green light reaches the light receiving layer 52 among the wavelength components of the incident light.
The light receiving layer 52 absorbs green light and generates electrons and holes. The generated electrons / holes flow into the pair of comb electrodes 72 and 74. Therefore, when the photoelectric conversion device 100 is used, only green light can be incident on the light receiving layer 52 from incident light including visible light including a blue light region to a green light region. The photoelectric conversion device 10 can selectively extract an optical signal corresponding to green light and obtain an electrical signal (current signal in this embodiment) corresponding to the optical signal. For this reason, in the photoelectric conversion device 100, disturbances due to optical signals of other wavelengths, external light, and the like are significantly suppressed, and the S / N ratio is high.
Note that a barrier layer may be provided between the light receiving layer 52 and the third filter layer 36 to prevent electrons and holes generated in the third filter layer 36 from flowing into the light receiving layer 52.
Further, another semiconductor layer may be provided on the surface of the third filter layer 36 to block visible light having other wavelengths.

(Method for manufacturing photoelectric conversion device 100)
Next, the manufacturing method of the photoelectric conversion apparatus 100 is demonstrated using FIG.
As shown in FIG. 7A, a substrate 22 made of sapphire is prepared. The surface a is selected as the surface of the substrate 22, and the surface is cleaned by organic cleaning and heat treatment.
First, while maintaining the temperature of the substrate 22 at 1100 ° C., hydrogen gas is supplied at a flow rate of 2 liters / minute, and the surface of the substrate 22 is vapor-phase etched.
Next, as shown in FIG. 7B, the temperature of the substrate 22 is lowered to 400 ° C., and the buffer layer 24 is formed over the substrate 22 by using the MOCVD method. At this time, hydrogen gas is supplied at 20 liters / minute, trimethylaluminum (TMAl) is supplied at 1.8 × 10 ⁻⁵ mol / minute as an aluminum raw material, and ammonia gas (NH ₃ ) is supplied at 10 liter / minute as a nitrogen raw material. It is preferable to supply in minutes.

Next, the temperature of the substrate 22 is maintained at 1150 ° C., and the base layer 62 is formed on the buffer layer 22 using the MOCVD method. At this time, trimethylgallium (TMG) can be suitably used as the gallium raw material, and ammonia gas (NH ₃ ) can be suitably used as the nitrogen raw material.
Next, the temperature of the substrate 22 is maintained at 730 ° C., and the light receiving layer 52 is formed on the base layer 62 using the MOCVD method. At this time, hydrogen gas or nitrogen gas is supplied at 20 liters / minute, trimethylgallium (TMG) is supplied at 1.0 × 10 ⁻⁴ mol / minute as a gallium raw material, and ammonia gas (NH ₃ ) is supplied as a nitrogen raw material. It is preferable to supply at 10 liters / minute and to supply trimethylindium (TMI) as an indium raw material at 0.5 × 10 ⁻⁴ mol / minute.
Next, the temperature of the substrate 22 is maintained at 850 ° C., and the third filter layer 36 is formed on the light receiving layer 52. At this time, hydrogen gas or nitrogen gas is supplied at 10 liters / minute, trimethylgallium (TMG) is supplied at 1.0 × 10 ⁻⁴ mol / minute as a gallium raw material, and ammonia gas (NH ₃ ) is supplied as a nitrogen raw material. It is preferable to supply at 10 liters / minute and to supply trimethylindium (TMI) at 0.2 × 10 ⁻⁴ mol / minute as an indium raw material.

Finally, as shown in FIG. 7C, the third filter layer 36 is removed along the formation sites of the pair of comb-tooth electrodes 72 and 74 using a photolithography technique and an etching technique. A pair of comb electrodes 72 and 74 are formed by depositing Ni on the surface of the light-receiving layer 52 that has been removed and exposed. The pair of comb electrodes 72 and 74 are simultaneously formed using the same manufacturing process.
Through these steps, the photoelectric conversion device 100 can be obtained.

(Third embodiment)
Next, the photoelectric conversion device 200 according to the third embodiment will be described. However, components that are substantially the same as those in the first embodiment or the second embodiment are denoted by the same reference numerals, and the description thereof may be omitted.
FIG. 8 is a cross-sectional view of a main part of the photoelectric conversion device 200.
As indicated by an arrow in FIG. 8, the photoelectric conversion device 200 receives incident light from above. Incident light extends from the ultraviolet light region to the visible light region including the green light region.
The photoelectric conversion device 200 includes a semiconductor stack of a substrate 22, a buffer layer 24, a base layer 62, a light receiving layer 52, a barrier layer 44, a fourth filter layer 37, and a fifth filter layer 38 in order from the opposite side to the incident surface. It has. The fourth filter layer 37 and the fifth filter layer 38 are provided on the incident surface side with respect to the light receiving layer 52. The barrier layer 44 is provided between the light receiving layer 52 and the fourth filter layer 37. A pair of first comb electrodes 72 and 74 are formed in electrical contact with the surface of the light receiving layer 52. The barrier layer 44, the fourth filter layer 37, and the fifth filter layer 38 are formed between the pair of first comb electrodes 72 and 74 on the surface of the light receiving layer 52. The barrier layer 44, the fourth filter layer 37, and the fifth filter layer 38 are formed so as to cover portions of the surface of the light receiving layer 52 other than those where the pair of first comb electrodes 72 and 74 are formed. It can be said that.
Further, a pair of second comb electrodes 76 and 78 are formed in electrical contact with the surface of the fourth filter layer 37. The fifth filter layer 38 is formed between the pair of second comb electrodes 76 and 78 on the surface of the fourth filter layer 37. It can be said that the fifth filter layer 38 is formed so as to cover a portion of the surface of the fourth filter layer 37 other than the pair of second comb electrodes 76 and 78.

The substrate 22 is formed using sapphire.
The buffer layer 24 is formed using aluminum nitride (AlN) having a thickness of about 0.05 μm.
The underlayer 62 is formed using gallium nitride (GaN) having a thickness of about 4.0 μm.

The light receiving layer 52 is formed using gallium nitride indium (In _0.4 Ga _0.6 N) having a thickness of about 0.020 μm. The light receiving layer 52 is made of a material having a narrower band gap than the band gaps of the fourth filter layer 37 and the fifth filter layer 38. Further, the band gap of the light receiving layer 52 is adjusted to a size capable of absorbing the wavelength of a visible light optical signal (which is light energy) to be received.

  The barrier layer 44 is formed using gallium nitride (GaN) having a thickness of about 0.015 μm. The material of the barrier layer 42 is a material having a wider band gap than the band gaps of the light receiving layer 52 and the fourth filter layer 37.

The fourth filter layer 37 is formed using gallium indium nitride (In _0.2 Ga _0.8 N) having a thickness of about 0.2 μm. As the material of the fourth filter layer 37, a material wider than the band gap of the light receiving layer 52 is employed. The band gap of the fourth filter layer 37 is adjusted to a size that absorbs the optical energy of visible light having a shorter wavelength than the visible light received by the light receiving layer 52.

The fifth filter layer 38 is formed using gallium nitride (GaN) having a thickness of about 0.2 μm. As the material of the fifth filter layer 38, a material having a wider band gap than the band gaps of the light receiving layer 52 and the fourth filter layer 37 is employed. The band gap of the fifth filter layer 38 is adjusted to a size that absorbs light energy of ultraviolet light.
Further, as will be described later, the fourth filter layer 37 can be said to be a second light receiving layer in terms of its function.

A pair of first comb electrodes 72 and 74 are formed on the surface of the light receiving layer 52. A constant potential is applied to the first comb electrode 72 and the first comb electrode 74, and a potential difference is formed between them. The pair of comb electrodes 72 and 74 are made of nickel (Ni) and have a thickness of 0.05 μm.
A pair of second comb electrodes 76 and 78 are formed on the surface of the fourth filter layer 37. A constant potential is applied to the second comb electrode 76 and the second comb electrode 78, and a potential difference is formed between them. The pair of comb electrodes 76 and 78 are made of nickel (Ni) and have a thickness of 0.05 μm.
The pair of comb-tooth electrodes 72 and 74 may employ either a conductive material transparent to visible light or an opaque conductive material. The pair of comb electrodes 76 and 78 may employ either a conductive material that is transparent to visible light or an opaque conductive material. One set of comb electrodes may be transparent and the other set of comb electrodes may be opaque. In consideration of both characteristics of the photoelectric conversion efficiency and the S / N ratio, it can be appropriately adopted.

Incident light incident on the photoelectric conversion device 200 is visible light including an ultraviolet light region to a green light region. The fifth filter layer 38 absorbs ultraviolet light having a short wavelength out of incident light including the ultraviolet light region to the green light region. Blue light and green light having a long wavelength pass through the fifth filter layer 38 and enter the fourth filter layer 37.
The fourth filter layer 37 absorbs blue light having a short wavelength and transmits green light having a long wavelength. Therefore, only the green light reaches the light receiving layer 52 among the wavelength components of the incident light. At this time, the fourth filter layer 37 absorbs blue light and generates electrons and holes. The generated electrons / holes flow into the pair of second comb electrodes 76 and 78. Thereby, in the 2nd comb-tooth electrodes 76 and 78, the optical signal according to blue light can be extracted, and the electric signal (in this example, current signal) according to it can be obtained.
Further, the light receiving layer 52 absorbs green light and generates electrons and holes. The generated electrons and holes flow into the pair of first comb electrodes 72 and 74. Thereby, in the 1st comb-tooth electrodes 76 and 78, the optical signal according to green light can be extracted, and the electrical signal (in this example, current signal) according to it can be obtained.
When the photoelectric conversion device 200 is used, it is possible to separate blue light and green light from incident light including visible light having a plurality of wavelengths and obtain an electrical signal corresponding to each optical signal. Optical signals having a plurality of wavelengths can be converted into electric signals by one photoelectric conversion device 200.
Note that a barrier layer may be provided between the fourth filter layer 37 and the fifth filter layer 38 to prevent electrons and holes generated in the fifth filter layer 38 from flowing into the fourth filter layer 37. Good.

(Method for manufacturing photoelectric conversion device 200)
Next, the manufacturing method of the photoelectric conversion apparatus 200 is demonstrated using FIG.
As shown in FIG. 9A, a substrate 22 made of sapphire is prepared. The surface a is selected as the surface of the substrate 22, and the surface is cleaned by organic cleaning and heat treatment.
First, while maintaining the temperature of the substrate 22 at 1100 ° C., hydrogen gas is supplied at a flow rate of 2 liters / minute, and the surface of the substrate 22 is vapor-phase etched.
Next, as shown in FIG. 9B, the temperature of the substrate 22 is lowered to 400 ° C., and the buffer layer 24 is formed on the substrate 22 by using the MOCVD method. At this time, hydrogen gas is supplied at 20 liters / minute, trimethylaluminum (TMAl) is supplied at 1.8 × 10 ⁻⁵ mol / minute as an aluminum raw material, and ammonia gas (NH ₃ ) is supplied at 10 liter / minute as a nitrogen raw material. It is preferable to supply in minutes.

Next, the temperature of the substrate 22 is maintained at 1150 ° C., and the base layer 62 is formed on the buffer layer 22 using the MOCVD method. At this time, trimethylgallium (TMG) can be suitably used as the gallium raw material, and ammonia gas (NH ₃ ) can be suitably used as the nitrogen raw material.
Next, the temperature of the substrate 22 is maintained at 730 ° C., and the light receiving layer 52 is formed on the base layer 62 using the MOCVD method. At this time, hydrogen gas or nitrogen gas is supplied at 20 liters / minute, trimethylgallium (TMG) is supplied at 1.0 × 10 ⁻⁴ mol / minute as a gallium raw material, and ammonia gas (NH ₃ ) is supplied as a nitrogen raw material. It is preferable to supply at 10 liters / minute and to supply trimethylindium (TMI) as an indium raw material at 0.5 × 10 ⁻⁴ mol / minute.
Next, the temperature of the substrate 22 is maintained at 850 ° C., and the barrier layer 44 is formed on the light receiving layer 52 using the MOCVD method. At this time, hydrogen gas or nitrogen gas is supplied at a rate of 20 liters / minute, trimethylgallium (TMG) is supplied as a gallium source at 1.5 × 10 ⁻⁴ mol / minute, and ammonia gas (NH ₃ ) is supplied as a nitrogen source. It is preferable to supply at 10 liters / minute.
Next, the temperature of the substrate 22 is maintained at 850 ° C., and the fourth filter layer 37 is formed on the barrier layer 44. At this time, hydrogen gas or nitrogen gas is supplied at 10 liters / minute, trimethylgallium (TMG) is supplied at 1.0 × 10 ⁻⁴ mol / minute as a gallium raw material, and ammonia gas (NH ₃ ) is supplied as a nitrogen raw material. It is preferable to supply at 10 liters / minute and to supply trimethylindium (TMI) at 0.2 × 10 ⁻⁴ mol / minute as an indium raw material.
Next, the temperature of the substrate 22 is maintained at 850 ° C., and the fifth filter layer 38 is formed on the fourth filter layer 37 using the MOCVD method. At this time, hydrogen gas or nitrogen gas is supplied at a rate of 20 liters / minute, trimethylgallium (TMG) is supplied as a gallium source at 1.5 × 10 ⁻⁴ mol / minute, and ammonia gas (NH ₃ ) is supplied as a nitrogen source. It is preferable to supply at 10 liters / minute.

Next, as shown in FIG. 9C, the fifth filter layer 38 is removed along the formation site of the pair of second comb electrodes 76 and 78 by using a photolithography technique and an etching technique. Ni is vapor-deposited on the surface of the fourth filter layer 37 exposed by removing the fifth filter layer 38 to form a pair of second comb electrodes 76 and 78. The pair of second comb electrodes 76 and 78 are simultaneously formed using the same manufacturing process.
Next, as shown in FIG. 9D, the fifth filter layer 38, the fourth filter layer 37, and the barrier layer 44 are paired with a pair of first comb electrodes 72, 74 using a photolithography technique and an etching technique. Remove along the site of formation. A pair of first comb electrodes 72 and 74 are formed by depositing Ni on the surface of the light-receiving layer 52 that has been removed and exposed. A pair of 2nd comb-tooth electrodes 72 and 74 are produced simultaneously using the same manufacturing process.
Through these steps, the photoelectric conversion device 100 can be obtained.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

The principal part sectional drawing of the photoelectric conversion apparatus of 1st Example is shown. The top view of the photoelectric conversion apparatus of 1st Example is shown. The band diagram of the semiconductor lamination of the photoelectric conversion device of the 1st example is shown. (A) The manufacturing process of the photoelectric conversion apparatus of 1st Example is shown. (B) The manufacturing process of the photoelectric conversion apparatus of 1st Example is shown. Sectional drawing of the principal part of the photoelectric conversion apparatus of 2nd Example is shown. The top view of the photoelectric conversion apparatus of 2nd Example is shown. (A) The manufacturing process of the photoelectric conversion apparatus of 2nd Example is shown. (B) The manufacturing process of the photoelectric conversion apparatus of 2nd Example is shown. (C) The manufacturing process of the photoelectric conversion apparatus of 2nd Example is shown. Sectional drawing of the principal part of the photoelectric conversion apparatus of 3rd Example is shown. (A) The manufacturing process of the photoelectric conversion apparatus of 3rd Example is shown. (B) The manufacturing process of the photoelectric conversion apparatus of 3rd Example is shown. (C) The manufacturing process of the photoelectric conversion apparatus of 3rd Example is shown. (D) The manufacturing process of the photoelectric conversion apparatus of 3rd Example is shown.

Explanation of symbols

22: substrate 24: buffer layer 32: first filter layer 34: second filter layer 36: third filter layer 37: fourth filter layer 38: fifth filter layer 42, 44: barrier layer 52: light receiving layer 62: lower Formations 72, 74: first comb electrodes 76, 78: second comb electrodes

Claims (6)

A photoelectric conversion device that converts light energy into electrical energy,
A light-receiving layer of a III-V compound semiconductor;
A pair of electrodes having a potential difference and being in electrical contact with the surface of the light receiving layer;
A filter layer of a III-V compound semiconductor provided on the incident surface side of the light receiving layer and having a wider band gap than the band gap of the light receiving layer;
The filter layer absorbs light having a shorter wavelength than light absorbed by the light receiving layer. The band width of the light receiving layer is adjusted so as to absorb the optical energy of visible light,
The photoelectric conversion device according to claim 1, wherein the filter layer has a band gap width adjusted so as to absorb visible light having a shorter wavelength than visible light absorbed by the light receiving layer.   The photoelectric conversion device according to claim 1, wherein the filter layer is formed between the pair of electrodes on the surface of the light receiving layer.   4. The photoelectric conversion device according to claim 1, wherein a barrier layer having a wider band gap than the light receiving layer and the filter layer is formed between the light receiving layer and the filter layer. The group III-V compound semiconductor is Al _X Ga _Y In _1-XY N (where 0 ≦ X ≦ 1, 0 ≦ Y ≦ 1, 0 ≦ 1-X−Y ≦ 1). Item 5. The photoelectric conversion device according to any one of Items 1 to 4.   6. The photoelectric conversion device according to claim 1, wherein a pair of electrodes having a potential difference is in electrical contact with the surface of the filter layer.

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