High-purity semi-insulating GaAs material for monolithic microwave integrated circuits

Abstract

Liquid-Encapsulated Czochralski (LEC) growth of large-diameter bulk GaAs crystals from pyrolytic boron nitride (PBN) crucibles has been shown to yield high crystal purity, stable high resistivities, and predictable direct ion-implantation characteristics. Undoped (≲low 1014cm-3chromium) and lightly Cr-doped (low 1015cm-3range) -GaAs crystals, synthesized and pulled from PBN crucibles contain residual shallow donor impurities typically in the mid 1014cm-3, exhibit bulk resistivities above 107Ω . cm, and maintain the high sheet resistances required for IC fabrication (>106Ω/□) after implantation anneal. Direct29Si channel implants exhibit uniform (± 5 percent) and predictable LSS profiles, high donor activation (75 percent), and 4800- to 5000-cm2/V . s mobility at the (1 to 1.5) × 1017cm-3peak doping utilized for power FET's. It has also been established that LEC crystals can provide the large-area, round