AN ANALYSIS OF THE PHOTORESPONSE OF A 6H-SIC UV PHOTODIODE

Ultraviolet (UV) photodiodes (PDs) with a p(+)/n/n mesa structure were fabricated using 6H-SiC epitaxial layers. The p(+)- and the n-layers were epitaxially grown on a 6H-SiC substrate by chemical-vapor deposit ion. SiH4 and C3H8 diluted with Hp were used as the source gases. B2H6 and N-2 gases diluted with H-2 were used for the p- and n-type doping , respectively. The photocurrent of the 6H-SiC PDs was measured as a f unction of incident wavelength in the wavelength range of 200 similar to 600 nm. The photocurrent was sensitive to the UV radiation in the r ange of 200 similar to 500 nm and reached a maximum value at 260 nm. T he distribution of the measured photocurrent of a GH-SIC PD was compar ed with that of the quantum efficiency (QE) calculated using a diffusi on model for the minority carriers in the n(+)/p junction in order to analyze the photocurrent of the PD. The contributions of the p(+)-laye r, the n-layer, the substrate, and the depletion region to the total Q E were 43.1, 18.7, 0.2, and 38.0%, respectively, between 200 nm and 35 0 nm. The distribution of the photocurrents was well explained by the diffusion model with the optical absorption of the depletion region in cluded.