4H-SiC SACM Avalanche Photodiode With Low Breakdown Voltage and High UV Detection Efficiency

In this paper, a high-performance 4H-SiC separated absorption charge multiplication ultraviolet avalanche photodiode (APD) with low breakdown voltage is designed and fabricated. The room temperature dark current of the APD remains at similar to 0.1 pA level (similar to 29 pA/ cm(-2)) when reverse bias is below 50 V and then rises by several orders of magnitude before avalanche breakdown occurs. An avalanche gain up to 10(6) is achieved at 67 V. Based on secondary ion mass spectroscopy measurement, the electric field distribution within the as-fabricated APD is numerically simulated. The ionization ratio of Al in the p-type charge control layer is estimated to be 40%. The frequency dispersion phenomenon in capacitance-voltage (C-V) measurement should be caused by structural defects existing within the APDs, which may also be the source of the enhanced dark current before avalanche breakdown. The room-temperature maximum quantum efficiency is similar to 80% at 270 nm with an ultraviolet (UV)/visible rejection ratio more than 10(4).