8 research outputs found
Comparison of Deep Centers in Semiinsulating Liquid-Encapsulated Czochralski and Vertical-Gradient Freeze GaAs
Threeâinch, semiâinsulating (SI) GaAs, grown by the vertical gradient freeze (VGF) technique, has been studied by IR absorption, temperatureâdependent dark current and Hallâeffect, thermally stimulated current (TSC), and photoinduced current transient spectroscopy and has been compared with undoped, SI GaAs, both Asârich and Gaârich, grown by the highâpressure liquidâencapsulated Czochralski method. The results clearly indicate that (1) the VGF GaAs contains less EL2, which suggests a less Asârich crystal stoichiometry; (2) in some VGF samples activation energies of 0.43 or 0.46 eV are deduced from temperatureâdependent carrier concentration or resistivity measurements, respectively, and (3) VGF samples often show a thermal quenching behavior in the TSC peak T5. There is evidence to suggest that the 0.43 eV center is related to VAs, and T5 to VGa