4H-silicon carbide detectors for low level ultraviolet detection

Ultraviolet radiation covers the wavelength from 400nm down to 10nm. The superior material properties of 4H-SiC make visible-blind, ultra sensitive and low noise UV photodetectors possible.;The major objective of this Ph.D. thesis research is to design and fabricate high performance 4H-SiC photodetectors for low-level UV detection. Schottky photodiodes, avalanche PIN photodiodes and avalanche phototransistors are studied for various applications.;In this study, the first 4H-SiC Schottky photodiode that can fully cover EUV to NUV range has been successfully fabricated. Ultralow leakage current, high quantum efficiency and high UV-to-visible rejection ratio have been achieved. The first 1x16 4H-SiC Schottky photodiode array with very large detection area has been successfully fabricated and characterized. A novel UV spectrographic system using the 4H-SiC Schottky photodiode array is demonstrated with a fine spectrum resolution.;4H-SiC single photon avalanche photodiode (SPAD) is studied for UV single photon detection. In this work, many challenging issues including bevel edge termination and ohmic contact have been addressed. The 4H-SiC SPADs show high gain, low dark count rate and good single photon detection efficiency (SPDE). The best 4H-SiC SPAD shows a high counting efficiency of 79% and 32.5% with a dark count rate of 125.3 kHz and 38.8 kHz at -119.4 V and -119 V, respectively. The first 4H-SiC SPAD array has been successfully fabricated and characterized. Only 1 pixel out of 33 pixels shows high leakage and high dark count rate. For all the good pixels working at -119.5V, the gain is greater than 10 6, the dark count rate is less than 100 kHz and the SPDE is more than 2%. The proton irradiation impact to 4H-SiC single photon avalanche diodes is investigated for the first time.;A novel 4H-SiC avalanche phototransistor structure is also studied in this research. The first 4H-SiC avalanche phototransistor is demonstrated with an optical gain greater than 4.5x104.