Deep-level defects near the surface of Be-doped GaAs grown by molecular beam epitaxy

Metal-semiconductor contacts on highly Be-doped GaAs layers grown by molecu lar beam epitaxy are used to examine deep electronic states by deep-level t ransient Fourier spectroscopy. Two hole traps at 0.40 and 0.70 eV are found , which are associated with the Ga-As (Ga atom on As site) defect. The conc entration versus depth profile demonstrates that the intrinsic defect is fo rmed in a 100 nm thick layer near the as-grown surface. Our experimental re sults confirm thermodynamical calculations for nearly Ga-rich conditions du ring growth. The Ga-As formation energy strongly decreases, when the Fermi level is shifted from the valence band edge to midgap position. The concent ration versus depth profile therefore reflects the change of the GaAs forma tion energy near the GaAs surface during growth. The energy to form Ga-As d efects at the surface of p-type GaAs is determined to be 1.1 eV, in full ag reement with theoretical results. (C) 1999 Elsevier Science B.V. All rights reserved.