SURFACE ELECTRON PROPERTIES OF 6H AND 15R MODIFICATIONS OF SILICON-CARBIDE

The temperature dependences of the surface potential phi(s) on the (00 01)Si and (0001)C surfaces of 6H- and 15R-SiC have been studied by the surface photovoltage method. It is found that the depletion layer is at all surfaces and phi(s) and phi(s)(T) values are determined by the physical-chemical conditions of the surfaces. For the (0001)Si surface s of 6H- and 15R-SiC oxidized electrolytically and etched in HF the ph i(s)(T) dependences have an N-like behaviour; for the (0001)C surfaces they have a V-like behaviour. Following from the Hall effect data and phi(s)(T) dependences we have carried out calculations of temperature dependences of the charge Q(s) in the surface electron states (SES) a nd the Fermi level position at surfaces. It is shown that the Q(s)(T) dependence with decreasing temperature is determined by charging SES w ith electrons and reconstruction of the SES system. We have found and studied the photomemory effect of the surface potential related to the capture of non-equilibrium holes by surface traps under illumination. The maximum trap concentration of 8 x 10(11) cm(-2) is observed at th e (0001)C surface of 15R-SiC and the minimum, at 2 x 10(11) cm(-2), is at the (0001)Si surface of 6H-SiC etched in HF.