Hetero-epitaxial β-SiC films were low-temperature grown onto <100> Si substrates using monomethylsilane (H_3Si-CH_3) precursors. In-situ doping was performed with NH_3, B_2H_6 TMA (trimethyl aluminum) and TEA (triethyl aluminum) precursors to obtain n- and p-type films, respectively. The electrical transport properties of the doped B-SiC films were characterized using electrical conductivity-. Hall-effect and thermopower measurements. In addition, photothermal deflection spectroscopy (PDS) and constant photocurrent measurements (CPM) were performed to obtain information about the density of defect-related localized states within the B-SiC bandgap. Nominally undoped films exhibited a relatively high level of n-type conductivity of about 1Ω~(-1) cm~(-1) which is likely to arise from unintentionally incorporated nitrogen or oxygen impurities. Nitrogen doping with NH_3 was able to raise the n-type conductivity up to about 150 Ω~(-1)cm~(-1). Upon doping with B_2H_6, overcompensation of the unintentionally incorporated donors could be achieved. At high boron concentrations of about 5×10~(20)cm~(-3), p-type conductivities of the order of 10~(-3) Ω~(-1)cm~(-1) could be obtained. Doping with high concentrations of TEA and TMA, at present did not result in p-type conduction or led only to a small overcompensation, respectively. This is attributed to the high n-type doping level in nominally undoped material.
展开▼
