GaN Metal-Insulator-Semiconductor Ultraviolet Photodetectors with a Gadolinium Fluoride Insulator

• Main Authors: HE,JIAN-FONG, 何建豐
• Other Authors: CHEN,CHIN-HSIANG
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/ur2x84

碩士 === 正修科技大學 === 電子工程研究所 === 107 === In recent years, ultraviolet detectors are widely reported due to the fact that gallium nitride (GaN) metal-semiconductor-metal (MSM) ultra-violet (UV) photodetectors (PDs) can operate with high performance because of the high-energy barrier junction which mainly exist between the interface of metal and semiconductor. This good energy barrier Schottky contact can provide a large energy barrier height, which makes the characteristics of the MSM photodetectors can be improved, but also to obtain a higher breakdown voltage, suppress the leakage current and improve the photocurrent-to-dark current ratio. To improve the device characteristics, the leakage current of the MSM photodetectors could be reduced by depositing and inserting a wide bandgap material between the interface of metal and semiconductor. There are already many materials which are used and published as the insulating layer for GaN. In the present study, gadolinium fluoride (GdF3) is used as the insulating layer for GaN materials. In this dissertation, in order to improve leakage current characteristic of UV detector devices, one insulating material such as GdF3 was introduced between metal electrode and semoconductor to fabricate GaN metal-insulator-semiconductor (MIS) ultraviolet photodetectors. The nickel (Ni) / gold (Au) thin film metal layer were evaporated and served as the semi-transparent electrode of GaN MSM PDs by using thermal evaporation deposition technology. The annealing ambient temperature was set to 500oC for this Ni/Au semi-transparent electrode. The wide bandgap GdF3 thin films with different thicknesses were applied and deposited onto the GaN substrates by using thermal evaporation system, and GaN MIS PDs with these GdF3 thin films with different thicknesses were also fabricated. It was found that in the experiments we can achieve the lower dark current and the larger photo-to-dark current ratios of GaN MIS PDs with the use of the GdF3 thin film. The reason was attributed to the large energy barrier height, which is originated from the use of GdF3 insulating layer located between metal and semiconductor. In addition, the use of GdF3 as an insulating layer can achieve a higher UV to visible rejection ratio, which can increase the detection efficiency of GaN MIS PDs.