Reduction of outdiffusion at the Ge/GaAs (100) interface by low temperature growth

Abstract

Ga outdiffusion into Ge layers grown epitaxially by molecular beam epitaxy was observed by secondary ion mass spectroscopy, x-ray photoemission spectroscopy, capacitance–voltage, and temperature dependent Hall-effect measurements. Films were initially grown at low rates (0.03–0.04 nm/s) and low temperatures (150–300 °C) on GaAs buffer layers on GaAs (100) substrates. The temperature and rate were then increased to 500 °C and 0.1 nm/s. The amount of Ga outdiffusion was greatest for films initially grown at 300 °C. No direct evidence of As outdiffusion at any temperature or Ga outdiffusion for initiation temperatures below 300 °C was found. Hall-effect measurements showed higher hole concentrations and greater levels of compensation in films initiated at 300 °C, consistent with outdiffusion of both Ga and As at this temperature. No degradation in the electrical characteristics of Ge–GaAs diodes was observed when the initial Ge growth temperature was reduced from 300 to 200 °C.