TWI390749B - Transparent photodetector and method for manufacture the same - Google Patents

Description

Transparent light detector and method of manufacturing same

The invention relates to a photodetector, in particular to a metal-semiconductor-metal (MSM) structured transparent photodetector with a zinc oxide film as an active layer and zinc oxide doped gold (ZnO: Au) as an electrode. .

With the development of space technology, the research of ultraviolet (UV) band detectors is more and more important. After the ultraviolet band was discovered by W. Ritter and WH Wollaston in 1801, some related research and applications have been Pay attention to it. The sun is the main source of ultraviolet light, and can be generally divided into three bands: UV-A (400 nm to 320 nm), UV-B (320 nm to 280 nm), and UV-C (below 280 nm). Since the ozone layer and other atmospheric gases absorb ultraviolet light from the sun, only ultraviolet light with a wavelength greater than 280 nm can reach the Earth's surface, so UV-A and UV-B ultraviolet light can affect human health and the Earth's ecosystem. Because UV light is widely used and researched, including ultraviolet astronomy, flame detection, missile detection, combustion technology, air-to-air communication, pollution monitoring, medicine, sterilization, and agriculture, it is efficient and reliable. The demand for detectors is increasing. At present, there are three conventional methods for converting a photo signal into a photodetector: a photomultiplier (PMT) using a vacuum tube, a photodetector using a germanium material, and a wide use. Light detector for energy gap materials. Among these three methods, the photomultiplier tube is high in cost, requires a high operating voltage, and the vacuum tube is easily broken. The twilight detector has the characteristics of easy fabrication, low cost, and low operating voltage. Further, the ultraviolet light detecting element is still constituted by a photodiode using a tantalum material. However, the energy gap limited by 矽 is only 1.2 eV at room temperature. The most sensitive wavelength of the bismuth-based photodiode does not fall in the ultraviolet region so that the response in the ultraviolet region is very low. Therefore, if a photodetector is made of a wide bandgap material, the material can have a larger bandgap (BandGap). Therefore, it is very suitable for the detection of ultraviolet light.

The energy gap of zinc oxide (ZnO) is about 3.3 eV, which happens to be in the blue to UV light band. The exciton binding energy of zinc oxide is about 60 meV, and the thermal perturbation at normal temperature (KT = 25 meV) cannot separate the excitons into free electrons and free holes, so the excitons of zinc oxide can exist at room temperature. In application, zinc oxide is widely used in semiconductor lasers, photodetectors, light-emitting diodes and piezoelectric sensors. In addition, zinc oxide has an essentially n-type semiconducting property, which is a very popular research topic for the development of new UV photodetectors. In addition, in view of the current awareness of environmental protection and green energy technology, the electrochromic sheet used in energy-saving glass is one of the most important components. Electrochromic technology refers to the use of an applied electric field to inject ions into a substance to cause a color change, thereby affecting the ability of the substance to resist light penetration. In addition to building energy-saving window materials to adjust the burden of lighting and air conditioning, the technology can be extended to a variety of low-end digital displays. However, the electrochromic sheet needs to be driven by an electric current, so an external power supply device is required. If the transparent light detector disclosed in the present invention can be used for power supply, it can be widely applied to the windshield and the sunroof of the automobile, thereby reducing the cost and environmental pollution caused by the external power supply. Therefore, in order to solve the above problems, it is desirable to provide a transparent light detector to overcome the disadvantages of the prior art. The job is the reason, the applicant is carefully tested and researched, and a perseverance spirit, finally developed a transparent photodetector with a transparent zinc oxide film as the active layer and a transparent conductive film as the electrode.

The main object of the present invention is to provide a transparent light detector. The photodetector is a metal-semiconductor-metal (MSM) structure, and the active layer is made of a zinc oxide thin film and the electrode is made of a transparent conductive film (ZnO: Au) and formed on a glass substrate to obtain a full light transmittance. Photodetector.

To achieve the above primary object, the present invention provides a transparent photodetector comprising a glass substrate, a zinc oxide buffer layer, a zinc oxide active layer, and a transparent electrode. The zinc oxide buffer layer is deposited on the glass substrate by sputtering, and has a thickness of 2 to 10 nm. The zinc oxide active layer is deposited on the zinc oxide buffer layer by sputtering, and has a thickness of 800 to 1200 nm. The transparent electrode is deposited on the active layer of zinc oxide by sputtering, and has a thickness of 80 to 120 nm. The zinc oxide buffer layer serves to increase absorption efficiency and prevent electron-hole diffusion from moving downward and blocking carriers from the glass substrate. The zinc oxide active layer is used to generate a photocurrent effect after illumination. The transparent electrode is used as a conductive medium for receiving the electron-hole pair of the active layer of the zinc oxide. Further, the transparent electrode is a rectangular finger-inserted electrode and is a film made of zinc oxide doped with gold (Au).

According to another object of a transparent photodetector of the present invention, the manufacturing method of the present invention comprises four steps: first, providing a glass substrate; second, forming a zinc oxide buffer layer on the glass substrate; and forming an oxidation a zinc active layer is on the zinc oxide buffer layer; and fourth, a transparent electrode is formed on the zinc oxide active layer.

According to another feature of a transparent photodetector of the present invention, the zirconium oxide active layer has a carrier mobility of between 30 and 150 cm ² /VS.

According to another feature of a transparent photodetector of the present invention, the transparent electrode is a film composed of zinc oxide doped gold (ZnO: Au).

According to another feature of a transparent photodetector of the present invention, the transparent electrode has a light transmittance of 80 to 90%.

According to another feature of a transparent photodetector of the present invention, the transparent electrode has a resistivity of between 2 x 10 ^-3 and 2 x 10 ^-4 Ωcm.

The above and other objects, features, and advantages of the present invention will become more apparent and understood.

While the invention may be embodied in various forms, the embodiments illustrated in the drawings It is not intended to limit the invention to the drawings and/or the particular embodiments described.

Referring to FIG. 1, a photo-detector 100 of a metal-semiconductor-metal (MSM) structure is shown. The photodetector 100 of the MSM structure comprises a glass substrate 110, a zinc oxide buffer layer 120, a zinc oxide active layer 130, and a transparent electrode 140. The glass substrate 110 has a thickness of about 200 μm. The zinc oxide buffer layer 120 is deposited on the glass substrate 110 by sputtering, and has a thickness of 2 to 10 nm and preferably 5 nm. The zinc oxide active layer 130 is deposited on the zinc oxide buffer layer 120 by sputtering, and has a thickness of 800 to 1200 nm and is preferably 950 nm; the gap value is about 3.3 and is a semiconductor doped without any impurities. material. The transparent electrode 140 is deposited on the zinc oxide active layer 130 by sputtering, and has a thickness of 80 to 120 nm and preferably 100 nm. The zinc oxide buffer layer 120 serves to increase absorption efficiency and prevent electron-hole diffusion from moving downward and blocking carriers from the glass substrate 110. The zinc oxide active layer 130 is used to generate a photocurrent effect after illumination. The transparent electrode 140 serves as a conductive medium for receiving the electron-hole pair of the zinc oxide active layer 130. Further, the transparent electrode 140 is a rectangular finger-inserted electrode and is a film made of zinc oxide doped with gold (Au). It should be noted that the actual average surface roughness of the zinc oxide active layer 130 is 3 to 25 nm and the carrier mobility is between 30 and 150 cm ² /VS. In a preferred embodiment of the present invention, the transparent electrode 140 has a carrier concentration of between 8×10 ¹⁸ and 6×10 ²⁰ cm ⁻³ , a light transmittance of 80 to 90%, and a resistivity of 2×. Between 10 ^-3 and 2 × 10 ^-4 Ωcm. The transparent photodetector 100 of the MSM structure can be applied substantially in the ultraviolet light band having a wavelength of about 370 nm.

Referring to FIG. 2, a photodetector 200 of a metal-insulator-metal (MIS) structure is shown. The MIS structure photodetector 200 includes a glass substrate 110, a zinc oxide buffer layer 120, a zinc oxide active layer 130, a germanium dioxide insulating layer 210, and a transparent electrode 140. The glass substrate 110 has a thickness of about 200 μm. The zinc oxide buffer layer 120 is deposited on the glass substrate 110 by sputtering, and has a thickness of 2 to 10 nm and preferably 5 nm. The zinc oxide active layer 130 is deposited on the zinc oxide buffer layer 120 by sputtering, and has a thickness of 800 to 1200 nm and preferably 950 nm. The zinc oxide active layer 130 has a band gap value of about 3.3 and is a semiconductor material that is free of any impurities. The ceria insulating layer 210 is formed on the zinc oxide active layer 130 by plasma-assisted chemical vapor deposition, and has a thickness of 3 to 8 nm and preferably 5 nm. The transparent electrode 140 is deposited on the ceria insulating layer 210 by sputtering, and has a thickness of 80 to 120 nm and preferably 100 nm. The zinc oxide buffer layer 120 serves to increase absorption efficiency and prevent electron-hole diffusion from moving downward and blocking carriers from the glass substrate 110. The zinc oxide active layer 130 is used to generate a photocurrent effect after illumination. The ceria insulating layer 210 is used to reduce the surface energy level of the zinc oxide film, reduce the low frequency internal gain phenomenon, reduce the dark current of the MIS structure photodetector 200, and prevent the diffusion effect inside the zinc oxide active layer 130 material. The transparent electrode 140 serves as a conductive medium for receiving the electron-hole pair of the zinc oxide active layer 130. Further, the transparent electrode 140 is a rectangular finger-inserted electrode and is a film made of zinc oxide doped with gold (Au). In a preferred embodiment of the present invention, the zirconium oxide active layer 130 has a carrier mobility of 30 to 150 cm ² /VS and an average roughness of 3 to 25 nm; the carrier concentration of the transparent electrode 140 is Between 8 × 10 ¹⁸ and 6 × 10 ²⁰ cm ^-3 , the light transmittance is 80 to 90%, and the specific resistance is between 2 × 10 ^-3 and 2 × 10 ^-4 Ωcm. The transparent light detector 200 of the MIS structure can be applied substantially in the ultraviolet light band having a light wavelength of about 370 nm.

In the manufacturing method, the process steps of the present invention are:

A. First, a glass substrate 110 is provided. The glass substrate 110 was a Corning Eagle 2000 series glass having a size of 2000 μm × 2000 μm × 200 μm (length, width and height). The cleaning step of the glass substrate 110 is: immersing in the Pirana solution for boiling for 1 hour, and then returning to the room temperature, then taking out the glass substrate 110 and washing it with deionized water several times; then immersing in the secondary deionized water to supersonicize After shaking for 15 minutes, it was blown dry with a nitrogen gun. Among them, the Pirana solution is configured by adding concentrated sulfuric acid (H ₂ SO ₄ ) to hydrogen peroxide (H ₂ O ₂ ) in a volume ratio of H ₂ SO ₄ :H ₂ O ₂ =3:1.

B. forming a zinc oxide buffer layer 120 on the glass substrate 110 by using a sputtering method with a power of 350 W to 700 W, an oxygen flow rate of 1.5 sccm to 3.0 sccm, and a chamber pressure of 10 ^-2 to 10 ^-3 torr and A film having a thickness of 2 to 10 nm is formed under the conditions of a cavity temperature of 100 to 300 °C. Among them, the condition is that the power is 350 W, the oxygen flow rate is 2 sccm, the chamber pressure is 10 ^-3 torr, and the chamber temperature is 200 °C.

C. forming a zinc oxide active layer 130 on the zinc oxide buffer layer 120, using a sputtering method at a power of 350 W to 700 W, an oxygen flow rate of 1.5 sccm to 3.0 sccm, and a chamber pressure of 10 ^-2 to 10 ^-3 A film having a thickness of 800 to 1200 nm is formed under the conditions of a reactor temperature of 100 to 300 ° C. Among them, the condition is that the power is 350 W, the oxygen flow rate is 2 sccm, the chamber pressure is 10 ^-3 torr, and the chamber temperature is 200 °C.

D. forming a transparent electrode 140 on the zinc oxide active layer 130, using a sputtering method at a power of 300 W to 700 W, an oxygen flow rate of 1 sccm to 3.0 sccm, a cavity pressure of 10 ^-2 to 10 ^-3 torr and a cavity A film having a zinc oxide doped gold (ZnO: Au) and having a thickness of 80 to 120 nm is formed at a body temperature of 150 to 250 °C. Among them, the power is 400W, the oxygen flow rate is 1.5sccm, the chamber pressure is 10 ^-3 torr and the chamber temperature is 250 °C.

The above process steps are based on the MSM structured photodetector 100. In the case of the MIS structured photodetector 200, a cerium oxide insulating layer 210 is formed on the zinc oxide active layer 130 by a plasma assisted chemical vapor deposition (PECVD) deposition method at a power of 100 W and an oxygen flow rate of 70 sccm. A film having a thickness of 5 nm was formed under the conditions of a cavity pressure of 10 ^-5 torr and a cavity temperature of 500 °C. The transparent electrode 140 is formed on the ceria insulating layer 210 by sputtering to form the MIS structured photodetector 200. It should be noted that the present invention uses a 13.56 MHz RF magnetron sputtering technique. The resistivity of the transparent electrode 140 is between 2×10 ^-3 and 2×10 ^-4 Ωcm, the carrier concentration is between 8×10 ¹⁸ and 6×10 ²⁰ cm ^-3 , and the carrier mobility is 20~. The distance between 55cm ² /VS and the light transmittance is 80-90%. The photocurrent of the MSM structured photodetector 100 of the present invention is between 4×10 ^-5 and 6×10 ^-2 , and the DC bias voltage is in the range of 0 to 10 V; the photocurrent of the MIS structured photodetector 200 is 4 Between ×10 ^-8 and 6×10 ^-4 , the DC bias voltage is in the range of 0 to 10V.

Please refer to FIG. 3, which shows a top view of the transparent electrode 140. The dotted line is the active area 150, which means the area where the incident photons are received. The transparent electrode 140 is a rectangular finger-inserted electrode having an area of the silicon oxide active layer 130 of 200 × 200 μm ² , a finger width (W) of 10 μm, and a finger gap (S) of 10 μm.

In summary, the present invention provides an MSM and MIS structure transparent photodetector 100, 200 and a method of fabricating the same. The active layer 130 is made of a zinc oxide thin film and the electrode is made of a transparent conductive film (ZnO: Au) and formed on the glass substrate 110 to obtain photodetectors 100 and 200 having full light transmittance. The transparent photodetector 100, 200 of the present invention provides sufficient driving current to supply the electrochromic sheet, which can be widely applied to the windshield and the sunroof of the automobile, thereby reducing the cost and environmental pollution caused by the external power source.

While the present invention has been described in its preferred embodiments, it is not intended to limit the scope of the invention, and various modifications and changes can be made without departing from the spirit and scope of the invention. As explained above, various modifications and variations can be made without departing from the spirit of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

100. . . Transparent light detector (MSM structure)

110. . . glass substrate

120. . . The buffer layer

130. . . Active layer

140. . . Transparent electrode

150. . . Active zone

200. . . Transparent light detector (MIS structure)

210. . . Insulation

Figure 1 shows the transparent photodetector of the MSM structure.

Figure 2 shows the transparent light detector of the MIS structure.

Figure 3 shows a top view of the transparent electrode.

100. . . Transparent light detector (MSM structure)

110. . . glass substrate

120. . . The buffer layer

130. . . Active layer

140. . . Transparent electrode

Claims (10)

A transparent photodetector comprising: a glass substrate; a zinc oxide buffer layer deposited on the glass substrate by sputtering; and a zinc oxide active layer deposited on the zinc oxide buffer layer by sputtering And a transparent electrode deposited on the active layer of zinc oxide by sputtering; wherein the transparent electrode is a rectangular finger-inserted electrode, and is doped with zinc oxide (Au), platinum (Pt), A thin film of a metal material of a group of copper (Cu) and silver (Ag). The transparent photodetector of claim 1, further comprising: a germanium dioxide insulating layer deposited between the active layer of the zinc oxide and the transparent electrode. The transparent photodetector according to claim 1, wherein the zinc oxide buffer layer has a thickness of 2 to 10 nm, the zinc oxide active layer has a thickness of 800 to 1200 nm, and the transparent electrode has a thickness of 80 to 120 nm. The transparent photodetector according to claim 1, wherein the transparent electrode is a film made of zinc oxide doped gold (ZnO: Au). The transparent photodetector according to claim 1, wherein the transparent electrode has a resistivity of between 2 × 10 ^-3 and 2 × 10 ^-4 Ωcm. A method for manufacturing a transparent photodetector, comprising the steps of: A. providing a glass substrate; B. forming a zinc oxide buffer layer on the glass substrate; C. forming a zinc oxide active layer on the zinc oxide buffer layer And D. form a transparent electrode on the active layer of zinc oxide. The manufacturing method according to claim 6, wherein the step (B) is performed by a sputtering method at a power of 350 W to 700 W, an oxygen flow rate of 1.5 sccm to 3.0 sccm, and a chamber pressure of 10 ^-2 to 10 ^- A film having a thickness of 2 to 10 nm is formed under conditions of ³ torr and a cavity temperature of 100 to 300 °C. The manufacturing method according to claim 6, wherein the step (C) is performed by a sputtering method at a power of 350 W to 700 W, an oxygen flow rate of 1.5 sccm to 3.0 sccm, and a chamber pressure of 10 ^-2 to 10 ^- A film having a thickness of 800 to 1200 nm is formed under conditions of ³ torr and a cavity temperature of 100 to 300 °C. The manufacturing method according to claim 6, wherein the step (D) is performed by a sputtering method at a power of 300 W to 700 W, an oxygen flow rate of 1 sccm to 3.0 sccm, and a chamber pressure of 10 ^-2 to 10 ^{-3 .} A thin film of zinc oxide doped with gold (ZnO: Au) and having a thickness of 80 to 120 nm is formed under the conditions of a reactor temperature of 150 to 250 ° C. The manufacturing method according to claim 6, wherein the transparent electrode is a rectangular finger-inserted electrode, wherein the zinc oxide active layer has an area of 200 × 200 μm ² , a finger width of 10 μm and a finger gap of 10 μm.