Substrate-impurities effects on GaAs MESFETs
The effects of background impurities in LEC and HB-grown, doped and undoped GaAs substrates on electron-concentration profiles and ion-implanted MESFET threshold voltages are modeled. For realizing the most steeply falling channel electron profiles, high concentrations of either deep or shallow acceptors are required. When background acceptor impurities are absent, the electron profiles follow the slowly falling ion-implant profiles, which are strongly influenced by ion channeling. The use of buriedp layers to give steeply falling profiles, and to reduce the dependence of MESFET threshold voltages on fluctuating acceptor impurities in GaAs is proposed.