Oxygen Doping of GaAs During Omvpe Controlled Introduction of Impurity Complexes

Abstract

AbstractGaAs epilayers have been grown by Organo-Metallic Vapor Phase Epitaxy using dimethylaluminum methoxide as a dopant source. This compound contains a strong aluminumoxygen bond which is thought to remain intact during low temperature deposition and result in the incorporation of Al-O as a complex. Incorporation of aluminum and oxygen was investigated by Secondary Ion Mass Spectroscopy as a function of growth conditions: growth temperature, growth rate, V/III ratio, reactor pressure and dopant mole fraction. High doping levels up to 1020 cm−3 (for both oxygen and aluminum) were achieved without degradation of surface morphology andlor precipitation of a second phase. Oxygen concentration is lower than that of aluminum for all investigated growth conditions but at low deposition temperatures oxygen/aluminum ratios approach 1, indicating that Al-O is incorporated as a pair. Infrared absorption measurements in the 600-1200 cm−1 range did not detect well known isolated oxygen localized vibrational modes (LVM). Also in layers grown at low temperatures the intensity of isolated aluminum LVM at 362 cm−1 is much smaller than the concentration obtained by SIMS. Both observations prove that oxygen not only is incorporated as an Al-O pair but remains bonded in the bulk of the layer. Low temperature photoluminescence measurements indicate that the A1-O complex is electrically active in GaAs, forms a deep level within the GaAs band gap, and serves as an efficient non-radiative recombination center. Near band edge luminescence intensity correlates well incorporation of oxygen. The Al-O pairs act as deep acceptors in GaAs and cause the compensation of shallow tellurium donors.