Numerical simulations of GaAs MESFETs with deep chromium acceptors in the semi-insulating substrate were made. The results were compared with those obtained for a case with deep donors such as EL2 centers and shallow acceptors. It was found that an acceptor density in the substrate is a predominant factor in determining current-voltage characteristics of GaAs MESFETs, whether the acceptor is deep or shallow. Potential profiles were, however, found to depend strongly on the nature of deep levels in the substrate, suggesting that different drain breakdown characteristics or different backgating effects may be observed between the two cases. To minimize short-channel effects in GaAs MESFETs, the substrate conduction must be reduced. For this purpose, the deep-acceptor density in the semi-insulating substrate should be made high.
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