TWI233214B - Structure for a gallium-nitride (GaN) based ultra-violet light detector - Google Patents

Abstract

A structure for a gallium-nitride (GaN) based ultra-violet light detector is provided. The structure contains a n-type contact layer, a light absorption layer, a light penetration layer, and a p-type contact layer, sequentially stacked on a substrate from bottom to top in this order. The layers are all made of aluminum-gallium-indium-nitride (AlGaInN) compound semiconductors. By varying the composition of aluminum, gallium, and indium, the layers, on one hand, can achieve the desired band gaps so that the light detector is highly responsive to an ultra-violet light of a specific wavelength. On the other hand, the layers have compatible lattice constants so that problems associated with excessive stress are avoided and high-quality epitaxial structure is obtained. The structure further contains a positive electrode, a light penetration contact layer, and a anti-reflective coating layer on the p-type contact layer, and a negative electrode on the n-type contact layer.

Description

1233214 IX. Description of the invention: [Technical field to which the invention belongs] The present invention relates to an ultraviolet light detector, and more particularly to an ultraviolet light detector structure using a gallium nitride-based compound semiconductor. [Prior technology] At present, there are three known methods of PhotoDetector that can convert optical signals into electrical signals. They are Photo-Multiplier (PMT) using vacuum tubes, and light using silicon materials. A detector, and a photodetector using a gallium nitride-based compound semiconductor. a ‘In the second approach, photomultiplier tubes are costly, require high operating voltages, and the vacuum officials are easily broken. The silicon photodetector has the characteristics of easy fabrication, low cost, and low operating voltage. Although the silicon photodetector has relatively good performance in detecting larger wavelengths and infrared light, it is less sensitive to shorter wavelengths. In contrast, 镓 t f 以, which uses gallium nitride-based compounds as the material, is a material that can have a large band gap (Band Gap), which is used for detection of external light. Furthermore, by controlling the formation of gallium nitride to change its energy gap, a photodetector for ultraviolet light with a specific wavelength can be manufactured. ί Figure: Nitrogen c, the response curve of the external photodetector. Such as the first UV recording He e series UV light detector, especially in the 300 ~ 37nm light detection cries benefit range = quite fast response, which is not achieved by the conventional silicon. Therefore, in applications requiring fast response, the nitrogen 1233214 gallium-based ultraviolet photodetector is providing excellent performance. One of the common problems with H gallium nitride-based semiconductor devices is that the lattice constants between adjacent half-body layers are too large. Because of this lattice structure, the excessive stress caused often makes the epitaxial structure of the semiconductor device good: and then affects its performance. In addition, gallium nitride-based ultraviolet light requires a large enough energy gap to reflect light in a specific wavelength range, and where it contacts the electrode, the energy gap cannot be too large. In addition, how to reduce the reflection of ultraviolet light on the surface of the two-dimensional optical fiber measured by nitriding, and how to improve its optical signal characteristics, is also the solution of whether the gallium nitride-based ultraviolet light detector has practical value. / 、 $ 肩 [Summary of the Invention] The structure of the gallium nitride-based ultraviolet photodetector can only solve the limitations and defects in the foregoing related technologies. Then, with the structure of the photodetector, the basic layer and the -Touch: layers, a light absorbing layer, and a light penetrating gallium indium nitride (AlaG'bli ^ if "body, all of which are composed of semiconductor materials with a specific composition. The composition of the composition of indium, these materials are aluminum, gallium, interstitial, and carrier-concentrated materials. M m 9 On the one hand, it can have all the energy that can be reacted; / Spirit for specific wavelengths of ultraviolet light The matching crystal constants, so that the body layer can have a high-quality lattice structure ==, the positive electrode, a light this structure further-including a 1233214 penetrating ohmic contact layer on the P-type contact layer, and An anti-reflection layer, and -negative electrode on n. The reflectivity of this anti-reflection layer to light with ultraviolet light wavelength is less than 30%, so that most of Ai f passes through the ohmic contact layer and enters the gallium nitride-based ultraviolet light inspection = σσ ° [Embodiment] The second diagram is not intended for the first embodiment of the structure of the ultraviolet light detector of the present invention. As shown in the second diagram, this embodiment is made of alumina / RPiane or A-Plane alumina Single crystal (sapphire) or carbonization = (SH ^ iC or 4H-SiC) is the substrate 10, and other materials that can be used for the substrate 10 include Si, ZnO, GaAs or spinel (MgAl204), or The crystal lattice constant is close to that of a single crystal oxide of a nitride semiconductor, and then an n-type contact layer 20 is formed on one side of the plate 10, and the !!-type contact layer 20 is composed of n-type doping, AlaGayni.a_bN (0 ^ a, bSl, a + b $ l) with a specific set of theta, the thickness is between 300 and 4,000A, and the growth temperature is between 700 ° C and 1200 ° C. Then, a light absorption layer 32 is formed on the n-type contact layer 20, and the light absorption layer 32 is made of undoped AlcG / dIni_c_d with a specific composition. Meal consisting of N (〇Sc, c ^ l, c + dSl), thickness between 100A ~ 10000A, growth temperature between 700 ° c ~ 1200 ° c, and covering part of the n-type contact layer 20 Surface. By adjusting its A1,

The light absorbing layer 32 has an energy gap of more than 3.4 electron volts (eV), so it can sensitively sense light in the ultraviolet light wavelength range (300nm ^ 370nm). On the part of the n-type contact layer 20 whose surface is not covered, a negative electrode 30 composed of Ti and A1 alloy is formed in this embodiment. In this embodiment, a light-transmitting layer 40 is formed on the light-absorbing layer. This light passes through 7 1233214. A superlattice structure composed of a stack of a plurality of layers, "The mother layer ® includes two layers, each having a thickness between 50 and 200 A, and the growth temperature between 700 and 120. c > a single layer between c. These two single layers are made of p-type doped

AleGafIni_e_fN and AlgGahIni_g_hN (〇 $ e, f, g, hsl, e + g + MI). The superlattice structure has a high carrier concentration and a high carrier mobility. Therefore, the ultraviolet light detector of the present invention has quite excellent electrical characteristics. Next, it is located above the light transmission layer 40. In this embodiment, a p-type contact layer 50 is formed. The p-type contact layer 50 is composed of p-type doped AliGajlmyNCOsijsi (i + jS1). 、 Growth temperature ^ ~~ 700. (: ~ 1200 ° C. Since the energy gap of the p-type contact layer 50 cannot be too wide to form a good ohmic contact with the electrode, and to avoid the problem of narrow-band gap nitride absorption, P-type contact The thickness of the layer 50 is between 20A and 2000A. Above the P-type contact layer 50, this embodiment further forms a positive electrode 60 and a light penetrating ohmic contact layer 62 that do not overlap each other. The positive electrode The 60 series is composed of an alloy of Ni and Au. The light penetrating ohmic contact layer 62 may be a metal conductive layer having a thickness between 20A and 200A, or a thickness between 200A and 3000A. Transparent conductive oxide layer. This metal conductive layer can be made of Ni / Au alloy, Ni / Pt alloy, Ni / Pd alloy, Ni / Co alloy, Pd / Au alloy, Pt / Au alloy, Ti / Au alloy, Cr / One of Au alloy, Sn / Au alloy, Ta / Au alloy, TiN, TiWNx (it 0), Wsiy (at 0), or other similar metal materials. This transparent conductive oxide layer can be composed of ΓΓΟ, CTO ,

ZnO: Al, ZnGa2〇4, Sn02: Sb, Ga203: Sn, AgIn〇2: Sn, In2〇3: Zn,

One of CuA102, LaCuOS, NiO, CuGa02, SrCu202, or other similar materials. 1233214 On the light penetrating ohmic contact layer 62, this embodiment then forms an anti-reflection layer 64 that does not overlap the positive electrode 60 to prevent incident light of ultraviolet rays from being reflected on the surface of the detector. The anti-reflection layer 64 may be made of one of Si02, SiN4, Ti02 and other materials, or a 5102/1 ^ 02 distributed Bragg reflector (DBR). The reflectance of this anti-reflection layer 64 to light in the wavelength range of ultraviolet light is less than 30%. Fig. F is an illustration of the second embodiment of the structure of the ultraviolet light detector of the present invention. As shown in the third figure, this embodiment is the same as the first embodiment = structure and growth method. The only difference is the material used in the light absorbing layer. In this embodiment, the light absorption layer 34 formed on the n-type contact layer 20 is composed of AlmGa ^ mNCO ^ i ^ l) doped with indium and having a specific composition. Because the indium-doped nitride easily flattens the interface, in addition to the advantages of the first embodiment, the quality of the light 34 can be changed to the ultraviolet and thallium detection of the third embodiment. As shown, the difference between this embodiment and the first and second embodiments in structure, material, and di- is the superlattice structure in the light absorbing layer, which is 36 and is composed of a stack of multiple layers. Between 50 people ~ 200A ', so,-the stacks include a single family with two layers and a thickness between. Both the growth temperature and the growth temperature are between 700 ° C and 1200 ° C. The AlGaIniON layer has a specific composition and undoped r + su), respectively. This book faJni-r-sN (0 Qiu, call set, ρ + Shangong, 100 people ~ ιοοοο Α the overall thickness of the receiving layer 36 is between layers 36, on the one hand can avoid the use of super crystal The light absorption of the lattice structure avoids the cracking problem of the single layer thick film using the high aluminum content nitride 1233214 in the second embodiment. On the other hand, the wider energy gap that can be achieved by the high aluminum superlattice structure can be adjusted. The ultraviolet light of the ice dagger (λ230nm) achieves the purpose of rapid response. The fifth figure of the ugly wavelength is the fourth schematic diagram of the structure of the ultraviolet light detector of the present invention. As shown in the fifth figure, this embodiment and the third implementation I = structure and growth mode. The only difference is that in the same f ^ t ^ η system, a superlattice structure composed of a stack of multiple layers, in which, a 38β 'layer λ〗, and the product type has a specific The composition is composed of indium doped ports u ahN and AlwGa ^ NCOSi ^ w). This super 38 ^ ^ '' has the characteristics of indium doped nitride easy to flatten the interface, to improve the epitaxial quality of the aluminum gallium nitride absorption layer, and the use of high aluminum-containing semiconductor wide band gap characteristics , So that the detection of 11 pairs of shorter wavelengths (λ-300nm) ultraviolet light response fast. Long = The above is only used to explain the best practice of the present invention. It is not intended to restrict the present invention in any form. Any modification to the present invention made in the spirit of Xiang Erming Any change or modification should be included in the scope of the present invention. [Brief description of the drawings], what is shown is not to provide specific embodiments for concretely describing the components described in this specification, and to explain the main purpose of the present invention, in order to understand the present invention. = A picture is a reaction curve of a gallium nitride based ultraviolet light detector. The first and second figures are not intended for the first embodiment of the structure of the ultraviolet light detector of the present invention. 1233214 The third diagram is a schematic diagram of the second embodiment of the structure of the ultraviolet light detector of the present invention. The fourth figure is a schematic view of the third embodiment of the structure of the ultraviolet light detector of the present invention. The fifth diagram is a schematic diagram of the fourth embodiment of the structure of the ultraviolet light detector of the present invention. [Description of main component 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 ohm Contact layer 64 Anti-reflective layer

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Claims (1)

1233214 10. Scope of patent application: 1. A gallium nitride-based ultraviolet light detector structure, including: a substrate made of alumina single crystal (Sapphire), 6H-SiC, 4H-SiC, Si, ZnO, GaAs, Spinel (MgAl204) and a single crystal oxide with a lattice constant close to that of a nitride semiconductor; an n-type contact layer, which is located on one side of the substrate, and is doped with an n-type AlaGablnubNCO ^ a ^ Sl, a + b £ l) with a specific composition and a thickness between 3000 and 40000A; a light absorption layer, which is located on the n-type contact layer and covers a part thereof The surface is made of lxGayln ^ yNCO ^^ d χ + γΐ). The thickness is between 100A and 10000A and has an energy gap greater than 3.4 electron volts. A negative electrode is located in the n-type contact layer and is not On the surface covered by the light absorption layer, it is composed of Ti and A1 alloy; a light transmission layer is a superlattice structure composed of one layer of a plurality of layers, which is located on the light absorption layer, and has a thickness larger than that of the light. The energy gap of the absorption layer, wherein each of the stacks includes two layers and the thickness is A single layer composed of AleGafIni e fN and AlgGahlihth NCOSe ^ g,} !: ^, e + fsi, g + h $ l) between 50A and 200A; The P-type contact layer is located on the light absorbing layer and is composed of p-type doped AliGajlnwN ^ Osi ^ 1, i + jsi), and the thickness is between 20A and 2000A; A light penetrating ohmic contact layer is a metal conductive layer on the p-type contact layer and covering part of its surface, and has a thickness between 20A and 20A, and a thickness between 20A and 200A. One of the transparent conductive oxide layers between 3000A; a positive electrode on the p-type contact layer, which is not covered by the light penetrating ohmic contact layer, and is composed of an alloy of Ni and Au; and An anti-reflection layer is located on the light-transmitting ohmic contact layer, and is composed of one of SiN4, Ti02, and Si02 / Ti02 dispersed Bragg reflectors. 12 1233214 2 · The gallium nitride-based ultraviolet light detector structure described in item 1 of the scope of the patent application, wherein the light absorption layer is made of undoped AlcGadln ^ -dNOKMSl, c + d $ l) composition. 3. The structure of the gallium nitride-based ultraviolet light detector according to item 1 of the scope of the patent application, wherein the light absorption layer is composed of indium doped and has a specific composition. 4. The gallium nitride-based ultraviolet photodetector structure according to item 1 of the scope of the patent application, wherein the light absorption layer is a superlattice structure composed of a stack of a plurality of layers, wherein each stack The layers each include two layers, each having a thickness between 50 and 200 A, and are composed of AlpGaqli ^ tqN and AlrGaJih + sNW ^^ AsAsl, p + qSl, r + d) with specific composition and undoped. Floor. 5. The gallium nitride-based ultraviolet photodetector structure according to item 1 of the scope of the patent application, wherein the light absorption layer is a superlattice structure composed of a stack of a plurality of layers, wherein each stack The layers each include two layers, each having a thickness between 50 and 200 A, and a single layer composed of AluGa ^ uN and AlwGaiwNiOSi ^ wSl) each having a specific composition and doped with indium. 6. The gallium nitride-based ultraviolet photodetector structure according to item 1 of the scope of patent application, wherein the metal conductive layer is made of Ni / Au alloy, Ni / Pt alloy, Ni / Pd alloy, Ni / Co alloy, It is composed of one of Pd / Au alloy, Pt / Au alloy, Ti / Au alloy, Cr / Au alloy, Sn / Au alloy, Ta / Au alloy, TiN, TiWNx ^ 0), and Wsiy (y2〇). 7. The structure of the gallium nitride-based ultraviolet photodetector 13 1233214 as described in item 1 of the scope of patent application, wherein the transparent conductive oxide layer is made of ITO, CTO, ZηO: A1, ZnGa2O4, SnO2: Sb, Ga2O3: Sn, AgIn0O2: Sn, 1n2O3 ... Zn, CuA102, LaCuOS, NiO, CuGa02, SrCu202.