Role of Electron Traps on the Thermal Conversion and Its Suppression for Liquid-Encapsulated Czochralski GaAs Single Crystals

Abstract
Concentration depth profiles of both carrier and electron traps shallower than EL2 are investigated for undoped liquid-encapsulated Czochralski GaAs single crystals after annealing in vacuum and ambient arsenic vapor pressure with As metal powders. Thermal conversion near the surface of semi-insulating GaAs annealed in vacuum at 900°C is suppressed by annealing with ambient arsenic pressure of 100 Torr. The carrier concentration depth profile of thermally converted GaAs, which is an initially semi-insulating substrate, depends not only on the concentration change of EL2 but also on that of native shallow acceptors and deep donors shallower than EL2.