Papers by Author: R.H. Hopkins

Abstract: II-VI has developed an Advanced PVT (APVT) process for the growth of nominally undoped (vanadium-free) semi-insulating 2” and 3” diameter 6H-SiC crystals with room temperature resistivity up to 1010 W·cm. The process utilizes high-purity SiC source and employs special measures aimed at the reduction of the impurity background. The APVT-grown material demonstrates concentrations of B and N reduced to about 2·1015cm-3. Wafer resistivity has been studied and correlated with Schottky barrier capacitance, yielding the density of deep compensating centers in 6H-SiC in the low 1015 cm-3 range for both ntype and p-type material. The nearly equal density of deep donors and deep acceptors ndicates that the centers responsible for the intrinsic compensation can be amphoteric. TheEPR density of spins from free carbon vacancies is about 1014 cm-3. It is also hypothesized that impurity-vacancy complexes can be present in the undoped material and participate in compensation.

Abstract: Semi-insulating 6H SiC substrates, 2”, 3” and 100mm in diameter, and n+ 4H SiC substrates, 2” and 3” in diameter, are grown at II-VI using the Advanced Physical Vapor Transport (APVT) technique [1]. The process utilizes high-purity SiC source and employs special measures aimed at the reduction of background contamination. Semi-insulating properties are achieved by precise vanadium compensation, which yields substrates with stable and uniform electrical resistivity reaching ~ 1011 Ω-cm and higher. Conductive n+ 4H SiC crystals with the spatially uniform resistivity of 0.02 W-cm are grown using nitrogen doping. Crystal quality of the substrates, their electrical properties and low temperature photoluminescence are discussed.