HIGH QUANTUM-EFFICIENCY 4H-SIC UV PHOTODIODE

We have designed a 4H-SiC UV photodiode having a n(+)/p/p structure se nsitive to ultraviolet radiation. The quantum efficiency of the photod iode was calculated by properly choosing parameters to increase the ul traviolet photoresponse. The wavelength at which the peak response occ urred could be well controlled by varying the junction depth, the geom etric structure of the photodiode, the doping concentrations of the n- and the p-layers, and the thickness of the anti-reflective layer. We expect a good photoresponse in this 4H-SiC homostructure for the wavel ength range of 200-380 nm. The highest internal quantum efficiency of the 4H-SiC photodiode came to about 92% for a peak at 257 nm. Also, th e calculated external quantum-efficiency curve of the 4H-SiC photodiod e shifted to shorter UV wavelength compared with the calculated one fo r 6H-SiC photodiode with nearly the same parameters. In addition, the peak of the external quantum efficiency of the 4H-SiC photodiode (abou t 90% at 257 nm) was higher by about 5% than that of a 6H-SiC photodio de (about 85% at 270 nm).