JP2006114564A - Gallium nitride based ultraviolet photodetector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultraviolet photodetector which uses a gallium nitride based semiconductor. <P>SOLUTION: A gallium nitride based ultraviolet photodetector includes an n-type contact layer, an optical absorption layer, a light transmission layer and a p-type contact layer upward in a substrate. Each of these semiconductor layers is configured with quaternary compound semiconductor materials of aluminum nitride gallium indium. By changing the composition of the components of aluminum, gallium, and indium of these materials, these semiconductor layer has a band gap which needs these semiconductor layers at one side. A reaction to an ultraviolet light of specific wavelength by this becomes specially sensitive. Moreover, it is one side that a lattice constant which these semiconductor layers matched is provided. Thereby, a matter related to a stress excess fault can be avoided. Moreover, the ultraviolet photodetector of a lattice structure of high quality is obtained. This structure further includes a positive electrode on a p-type contact layer, a light transmission ohm contact layer, a reflective prevention layer and a negative electrode on an n-type contact layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultraviolet light detector, and more particularly to a structure of an ultraviolet light detector using a gallium nitride based semiconductor.

  Currently, a photo detector that converts an optical signal into an electrical signal (Photo Detector) uses a photomultiplier (PMT) that employs a vacuum tube, a photodetector that uses a silicon material, and a gallium nitride based semiconductor. There are three types of photodetectors.

  Of these three types of photodetectors, the photomultiplier tube is expensive to manufacture, requires a high operating voltage, and is easily damaged. Silicon photodetectors are easy to manufacture, have low manufacturing costs, and low operating voltage. However, although silicon photodetectors have significantly better performance for detecting large wavelengths of visible and infrared light, they are less sensitive to short wavelength ultraviolet light. In contrast, a photodetector made of a gallium nitride compound is very suitable for detecting ultraviolet light because the material has a relatively large band gap. Further, by controlling the composition of the gallium nitride compound, the band gap can be modified, and a photodetector for ultraviolet light in a specific wavelength range can be manufactured.

  FIG. 1 is a reaction curve diagram of a gallium nitride ultraviolet light detector. Gallium nitride based ultraviolet photodetectors have a fairly rapid reaction, particularly in the 300-370 nm ultraviolet wavelength range, which cannot be achieved with known silicon photodetectors. Thus, the gallium nitride based ultraviolet light detector can provide an excellent expression in an application environment that requires a rapid reaction.

  One common problem with known gallium nitride semiconductor devices is that the lattice constant difference between adjacent semiconductor layers is too large. For this reason, an excessive stress is formed due to the difference in the lattice structure, which causes the epitaxial structure of the semiconductor device to be defective, thereby affecting the performance expression. In addition, gallium nitride-based ultraviolet light detectors, on the other hand, have a large band gap and must respond to ultraviolet light in a specific wavelength range. I can't get it. For this reason, how to reduce the reflection of ultraviolet light on the surface of a gallium nitride ultraviolet detector and how to improve its photoelectric conversion characteristics has been solved because the gallium nitride ultraviolet photodetector has practical value. It must be a problem.

  The present invention provides a kind of gallium nitride-based ultraviolet light detector and solves the limitations and disadvantages in the related art described above.

The invention of claim 1 is a gallium nitride based ultraviolet photodetector,
A substrate formed of sapphire, 6H—SiC, 4H—SiC, Si, ZnO, GaAs, spinel (MgAl ₂ O ₄ ), or a single crystal oxide whose lattice constant approaches a nitride semiconductor;
Located on one side surface of the substrate, it is made of n-type doped aluminum gallium indium nitride (Al _a Ga _b In _1-ab N, 0 ≦ a, b <1, a + b ≦ 1) having a specific composition and having a thickness of An n-type contact layer between 3000 and 40000,
Located on the n-type contact layer, covers the upper surface of a part of the n-type contact layer, and forms aluminum gallium indium nitride (Al _x Ga _y In _1-xy N, 0 ≦ x, y <1, x + y ≦ 1), a light absorption layer having a thickness between 100 Å and 10000 あ り and having a band gap greater than 3.4 eV;
A negative electrode made of an alloy of Ti and Al, located on the upper surface of the n-type contact layer, uncoated with the light absorption layer;
A superlattice structure that is formed on a plurality of layers and is located on the light absorption layer, has a larger band gap than the light absorption layer, each layer includes two layers, and the thickness of the single layer is is between 50Å~200Å either, p-type doped _{Al e Ga f in 1-ef} N and _{Al g Ga h in 1-gh} N (0 ≦ e of each specific composition, f, g, h ≦ 1, e + f ≦ 1, g + h ≦ 1), a light-transmitting layer;
It is located on the light absorption layer, is composed of p-type doped Al _i Ga _j In _1-ij N (0 ≦ i, j ≦ 1, i + j ≦ 1) and has a thickness of 20 to 2000 mm. A p-type contact layer,
One of a metal conductive layer located on the p-type contact layer and covering a part of its surface and having a thickness of 20 to 200 mm and a transparent conductive oxide layer having a thickness of 200 to 3000 mm. A light transmissive ohmic contact layer;
A positive electrode located in an uncovered portion of the light-transmitting ohmic contact layer on the upper surface of the p-type contact layer and formed of an alloy of Ni and Au;
An antireflection layer located on the light-transmitting ohmic contact layer and formed of any one of a distributed Bragg reflector (DBR) of SiO ₂ , SiN ₄ , TiO ₂ SiO ₂ / TiO ₂ ; A gallium nitride-based ultraviolet photodetector characterized by comprising:
According to a second aspect of the present invention, in the gallium nitride-based ultraviolet photodetector according to the first aspect, the light absorption layer is undoped and has a specific composition Al _c Ga _d In _1-cd N (0 ≦ c, d ≦ 1) , C + d ≦ 1), a gallium nitride ultraviolet light detector is provided.
The invention of claim 3 is the gallium nitride ultraviolet photodetector according to claim 1, wherein the light absorption layer is composed of Al _m Ga _1-m N, 0 ≦ m ≦ 1) having a specific composition. And a gallium nitride ultraviolet light detector.
A fourth aspect of the present invention is the gallium nitride-based ultraviolet photodetector according to the first aspect, wherein the gallium nitride based ultraviolet photodetector has a superlattice structure composed of a plurality of stacked layers, and each stacked layer includes two single layers, and the thickness of the single layer Both are comprised of Al _u Ga _1-u N and Al _w Ga _1-w N (0 ≦ u, w ≦ 1) having a specific composition of undoped between 50 and 200 mm. A gallium nitride ultraviolet light detector is used.
A fifth aspect of the invention is the gallium nitride based ultraviolet light detector according to the first aspect of the present invention, which is a superlattice structure composed of a plurality of laminated layers, each laminated layer comprising two single layers, and the thickness of the single layer. Both are comprised of Al _u Ga _1-u N and Al _w Ga _1-w N (0 ≦ u, w ≦ 1) having a specific composition of indium dope between 50 to 200 mm. The gallium nitride ultraviolet light detector is used.
A sixth aspect of the present invention is the gallium nitride based ultraviolet photodetector according to the first aspect, wherein the metal conductive layer comprises a Ni / Au alloy, a Ni / Pt alloy, a Ni / Pd alloy, a Ni / Co alloy, or a Pd / Au alloy. , Pt / Au alloy, Ti / Au alloy, Cr / Au alloy, Sn / Au alloy, Ta / Au alloy, TiN, TiWN _x (X ≧ 0), Wsi _y (y ≧ 0) This is a gallium nitride ultraviolet light detector.
The invention according to claim 7 is the gallium nitride based ultraviolet light detector according to claim 1, wherein the transparent conductive oxide layer is made of ITO, CTO, ZnO: Al, ZnGa ₂ O ₄ , SnO ₂ : Sb, Ga ₂ O ₃ : Sn. A gallium nitride-based ultraviolet photodetector characterized by being any one of AgInO ₂ : Sn, In ₂ O ₃ : Zn, CuAlO ₂ , LaCuOS, NiO, CuGaO ₂ , and SrCu ₂ O ₂ .

The gallium nitride based ultraviolet light detector submitted by the present invention is provided with an n-type contact layer, a light absorption layer, a light transmission layer, and a p-type contact layer in this order on a substrate. Each of these semiconductor layers is made of a quaternary compound semiconductor material of aluminum gallium indium nitride (Al _a Ga _b In _1-ab N, 0 ≦ a, b ≦ 1, a + b ≦ 1). By modifying the aluminum, gallium, and indium component composition of these materials, these semiconductor layers have the necessary band gap, which makes the response to ultraviolet light of specific wavelengths particularly sensitive, These semiconductor layers have matching lattice constants, thereby avoiding problems related to excessive stress and obtaining a high-quality lattice-structured ultraviolet photodetector.

  The structure further comprises a positive electrode on the p-type contact layer, a light transmissive ohmic contact layer, an antireflection layer, and a negative electrode on the n-type contact layer. This antireflection layer has a light reflectance of less than 30% in the ultraviolet wavelength range (smaller than 365 nm), and most of the light passes through the light-transmitting ohmic contact layer and enters the gallium nitride-based ultraviolet photodetector.

FIG. 2 is a display diagram of the first embodiment of the gallium nitride ultraviolet detector of the present invention. As shown in FIG. 2, in this embodiment, C-Phane, R-Plane, A-Plane sapphire or silicon carbide (6H-SiC or 4H-SiC) is used as the substrate 10, and others that can be used for the substrate 10. Examples of the material include Si, ZnO, GaAs, spinel (MgAl ₂ O ₄ ), or a single crystal oxide whose lattice constant approaches that of a nitride semiconductor. Thereafter, an n-type contact layer 20 is formed on one side surface of the substrate 10, and the n-type contact layer 20 is n-type doped, and Al _a Ga _b In _1-ab N (0 ≦ a, b ≦ 1) having a specific composition. , A + b ≦ 1), the thickness is between 3000 and 40000 mm, and the growth temperature is between 700 and 1200 degrees Celsius. Thereafter, a light absorption layer 32 is formed on the n-type contact layer 20, and this light absorption layer 32 is undoped and has a specific composition of Al _c Ga _d In _1-cd N (0 ≦ c, d ≦ 1, c + d). ≦ 1), the thickness is between 100 to 10,000 °, the growth temperature is between 700 to 1200 degrees centigrade, and the surface of a part of the n-type contact layer 20 is covered. By adjusting the material composition of Al, Ga, and In, the light absorption layer 32 has a band gap larger than 3.4 electron volts (eV), thereby allowing light in the ultraviolet wavelength range (300 nm ≦ λ ≦ 370 nm). Can be detected sharply. In this embodiment, a negative electrode 30 made of Ti and Al alloy is also formed in the uncovered portion of the surface of the n-type contact layer 20.

In this embodiment, a light transmission layer 40 is formed on a light absorption layer, and this light transmission layer 40 has a superlattice structure formed by stacking a plurality of layers (≧ 2). The two thicknesses are both 50 to 200 mm, and the growth temperature comprises a single layer between 700 and 1200 degrees Celsius. The two respective monolayer certain component and p-type doped _{Al e Ga f In 1-ef} N and _{Al g Ga h In 1-gh} N (0 ≦ e, f, g, h ≦ 1, e + f ≦ 1, g + h ≦ 1). The superlattice structure has a high carrier concentration and a high carrier mobility, so that the gallium nitride-based ultraviolet photodetector of the present invention has considerably excellent electrical characteristics.

Subsequently, a p-type contact layer 50 is formed above the light transmission layer 40 in this embodiment. This p-type contact layer 50 is made of p-type doped Al _i Ga _j In _1-ij N (0 ≦ i, j ≦ 1, i + j ≦ 1) having a specific composition, and its growth temperature is from 700 degrees Celsius to 1200 degrees Celsius. Between degrees. The band gap of the p-type contact layer 50 is not so wide that a good ohmic contact can be formed with the electrode, the problem of light absorption of the thin band gap nitride material is prevented, and the thickness of the p-type contact layer 50 is 20 mm or more. It is between 2000cm.

In this embodiment, a positive electrode 60 and a light transmission ohmic contact layer 62 that do not overlap each other are formed above the p-type contact layer 50. The positive electrode 60 is made of an alloy of Ni and Au. The light transmission ohmic contact layer 62 is a metal conductive layer having a thickness of 20 to 200 mm or a transparent conductive oxide layer having a thickness of 200 to 3000 mm. This metal conductive layer is made of Ni / Au alloy, Ni / Pt alloy, Ni / Pd alloy, Ni / Co alloy, Pd / Au alloy, Pt / Au alloy, Ti / Au alloy, Cr / Au alloy, Sn / Au alloy, One of Ta / Au alloy, TiN, TiWN _x (X ≧ 0), Wsi _y (y ≧ 0), or other similar metal material is used. This transparent conductive oxide layer is made of ITO, CTO, ZnO: Al, ZnGa ₂ O ₄ , SnO ₂ : Sb, Ga ₂ O ₃ : Sn, AgInO ₂ : Sn, In ₂ O ₃ : Zn, CuAlO ₂ , LaCuOS, NiO, It is either CuGaO ₂ or SrCu ₂ O ₂ , or other similar metal material.

In this embodiment, an antireflection layer 64 that does not overlap with the positive electrode 60 is formed on the light transmission ohmic contact layer 62 to prevent the incident ultraviolet light from being reflected from the surface of the detector. The antireflection layer 64 is made of any material such as SiO ₂ , SiN ₄ , or TiO _2, or is made of a distributed Bragg reflector (DBR) of SiO ₂ / TiO ₂ . The reflectance of the antireflection layer 64 with respect to light in the ultraviolet wavelength range is lower than 30%.

FIG. 3 is a display diagram of a second embodiment of the gallium nitride based ultraviolet photodetector of the present invention. As shown in FIG. 3, this embodiment and the first embodiment have the same structure and growth method. The only difference is the material used for the light absorbing layer. In this embodiment, the light absorption layer 34 formed on the n-type contact layer 20 is made of indium-doped Al _m Ga _1-m N (0 ≦ m ≦ 1) having a specific composition. Since indium-doped nitride has a flat interface, the light absorption layer 34 has the advantages of the first embodiment and further improves the epitaxial crystal quality.

FIG. 4 is a display diagram of a third embodiment of the gallium nitride based ultraviolet photodetector of the present invention. As shown in FIG. 4, this embodiment and the first and second embodiments have the same structure and growth method. The only difference is the structure, material and growth method of the light absorption layer. In this embodiment, the light absorption layer 36 formed on the n-type contact layer 20 has a superlattice structure composed of a plurality of layers, each of which includes two layers, All the thicknesses are between 50 and 200 and the growth temperature is between 700 and 1200 degrees Celsius. The two monolayers each specific composition and undoped _{Al p Ga q In 1-pq} N and _{Al r Ga s In 1-rs} N (0 ≦ q, p, r, s ≦ 1, q + q ≦ 1, r + s ≦ 1). The total thickness of the light absorption layer 36 is between 100 to 10,000 mm. The light absorption layer 36 having a superlattice structure employed in this embodiment, on the other hand, solves the problem of cracks in the single-layer thick film of the high aluminum content nitride employed in the previous two embodiments. With the wider band gap that can achieve a high aluminum content nitride superlattice structure, the objective of rapid reaction can be achieved for ultraviolet light of shorter wavelengths (λ = 300 nm).

FIG. 5 is a display diagram of a fourth embodiment of the gallium nitride based ultraviolet photodetector of the present invention. As shown in FIG. 5, this embodiment and the third embodiment have the same structure and growth method. The only difference is in the materials used for the light absorbing layer. In this embodiment, the light absorption layer 38 formed on the n-type contact layer 20 has a superlattice structure composed of a plurality of layers, each of which includes two layers and has a specific composition. It is composed of indium-doped Al _u Ga _1-u N and Al _w Ga _1-w N (0 ≦ u, w ≦ 1). This superlattice-structured light absorption layer 38 can avoid the problem of cracking of a single layer thick film of nitride with a high aluminum content, and on the other hand, due to the characteristics that the interface of the indium-doped nitride can be easily flattened, The epitaxial crystal quality of the aluminum gallium nitride light absorption layer can be improved and the wide band gap characteristics of the nitride semiconductor material with high aluminum content can be used to make the detector respond to ultraviolet light with a shorter wavelength (λ = 300 nm) Can be fast.

  The above is a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any modification or alteration in detail that can be made based on the present invention shall fall within the scope of the claims of the present invention. .

It is a reaction curve figure of a gallium nitride system ultraviolet light detector. It is a display figure of 1st Example of the gallium nitride type ultraviolet light detector of this invention. It is a display figure of 2nd Example of the gallium nitride type ultraviolet light detector of this invention. It is a display figure of 3rd Example of the gallium nitride type ultraviolet light detector of this invention. It is a display figure of 4th Example of the gallium nitride type ultraviolet light detector of this invention.

Explanation of symbols

10 substrate 20 n-type contact layer 30 negative electrode 32 light absorption layer 34 light absorption layer 36 light absorption layer 38 light absorption layer 40 light transmission layer 50 p-type contact layer 60 positive electrode 62 light transmission ohmic contact layer 64 antireflection layer

Claims (7)

In the gallium nitride based ultraviolet light detector,
A substrate formed of sapphire, 6H—SiC, 4H—SiC, Si, ZnO, GaAs, spinel (MgAl ₂ O ₄ ), or a single crystal oxide whose lattice constant approaches a nitride semiconductor;
Located on one side surface of the substrate, it is made of n-type doped aluminum gallium indium nitride (Al _a Ga _b In _1-ab N, 0 ≦ a, b <1, a + b ≦ 1) having a specific composition and having a thickness of An n-type contact layer between 3000 and 40000,
Located on the n-type contact layer, covers the upper surface of a part of the n-type contact layer, and forms aluminum gallium indium nitride (Al _x Ga _y In _1-xy N, 0 ≦ x, y <1, x + y ≦ 1), a light absorption layer having a thickness between 100 Å and 10000 あ り and having a band gap greater than 3.4 eV;
A negative electrode made of an alloy of Ti and Al, located on the upper surface of the n-type contact layer, uncoated with the light absorption layer;
A superlattice structure that is formed on a plurality of layers and is located on the light absorption layer, has a larger band gap than the light absorption layer, each layer includes two layers, and the thickness of the single layer is is between 50Å~200Å either, p-type doped _{Al e Ga f in 1-ef} N and _{Al g Ga h in 1-gh} N (0 ≦ e of each specific composition, f, g, h ≦ 1, e + f ≦ 1, g + h ≦ 1), a light-transmitting layer;
It is located on the light absorption layer, is composed of p-type doped Al _i Ga _j In _1-ij N (0 ≦ i, j ≦ 1, i + j ≦ 1) and has a thickness of 20 to 2000 mm. A p-type contact layer,
One of a metal conductive layer located on the p-type contact layer and covering a part of its surface and having a thickness of 20 to 200 mm and a transparent conductive oxide layer having a thickness of 200 to 3000 mm. A light transmissive ohmic contact layer;
A positive electrode located in an uncovered portion of the light-transmitting ohmic contact layer on the upper surface of the p-type contact layer and formed of an alloy of Ni and Au;
An antireflection layer located on the light-transmitting ohmic contact layer and formed of any one of a distributed Bragg reflector (DBR) of SiO ₂ , SiN ₄ , TiO ₂ SiO ₂ / TiO ₂ ;
A gallium nitride ultraviolet light detector characterized by comprising: 2. The gallium nitride based ultraviolet light detector according to claim 1, wherein the light absorption layer is undoped and composed of Al _c Ga _d In _1-cd N (0 ≦ c, d ≦ 1, c + d ≦ 1) having a specific composition. A gallium nitride-based ultraviolet photodetector, characterized in that 2. The gallium nitride-based ultraviolet detector according to claim 1, wherein the light absorption layer is composed of Al _m Ga _1-m N, 0 ≦ m ≦ 1) having a specific composition. Photo detector. 2. The gallium nitride based ultraviolet light detector according to claim 1, wherein the gallium nitride based ultraviolet light detector has a superlattice structure composed of a plurality of laminated layers, each laminated layer comprising two single layers, each of which has a thickness of 50 to 200 mm. A gallium nitride based ultraviolet photodetector characterized by comprising Al _u Ga _1-u N and Al _w Ga _1-w N (0 ≦ u, w ≦ 1) having a specific composition of undoped . 2. The gallium nitride based ultraviolet light detector according to claim 1, wherein the gallium nitride based ultraviolet light detector has a superlattice structure composed of a plurality of laminated layers, each laminated layer comprising two single layers, each of which has a thickness of 50 to 200 mm. Gallium nitride based ultraviolet light detection, characterized in that it is composed of indium-doped Al _u Ga _1-u N and Al _w Ga _1-w N (0 ≦ u, w ≦ 1) vessel. 2. The gallium nitride based ultraviolet light detector according to claim 1, wherein the metal conductive layer comprises a Ni / Au alloy, a Ni / Pt alloy, a Ni / Pd alloy, a Ni / Co alloy, a Pd / Au alloy, a Pt / Au alloy, Ti / Gallium nitride characterized by being formed of any one of / Au alloy, Cr / Au alloy, Sn / Au alloy, Ta / Au alloy, TiN, TiWN _x (X ≧ 0), and Wsi _y (y ≧ 0) System ultraviolet light detector. 2. The gallium nitride based ultraviolet light detector according to claim 1, wherein the transparent conductive oxide layer is made of ITO, CTO, ZnO: Al, ZnGa ₂ O ₄ , SnO ₂ : Sb, Ga ₂ O ₃ : Sn, AgInO ₂ : Sn, In ₂ O ₃ : A gallium nitride based ultraviolet photodetector characterized by being any one of Zn, CuAlO ₂ , LaCuOS, NiO, CuGaO ₂ , and SrCu ₂ O ₂ .

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