Observations Concerning Radiative Efficiency and Deep-Level Luminescence in <i>n</i>-Type GaAs Prepared by Liquid-Phase Epitaxy

Abstract

A study was made of n-type GaAs prepared by liquid-phase epitaxy doped with Si, Ge, Sn, Te, and Se by photoluminescence and Te-doped material by transmission-electron microscopy. A broad emission band centered at 1.2 eV (band B) is observed in LPE materials doped with group VI elements. Band B increases in intensity relative to the bandgap radiation with increasing dopant concentration in the 1018 cm−3 range. It is suggested that the recombination centers responsible for band B are the neutral (VGa+3 Te) complexes postulated by Vieland and Kudman, and that these represent the solid solution of Ga2Te3 in GaAs. With increasing dopant content, the solubility limit is eventually exceeded, and precipitates of this compound are then formed. These have been observed and identified by transmission-electron microscopy. The radiative efficiency falls off sharply with increasing dopant content beyond 2–3×1018 cm−3 in materials doped with Se and Te. It is suggested that this fall off is partly due to nonradiative recombination via small precipitates, each containing on the order of 1000 dopant atoms.