Identification of donors in vapor grown indium phosphide

Abstract

We report well resolved substructure in the ‘‘two electron’’ satellite (TES) near band-gap photoluminescence (PL) of excitons bound to shallow donors in InP, observable in high magnetic fields above ∼3 T. This substructure arises from differences in the central cell corrections to the binding energies of different donor species, resolved here for the first time in PL spectra for InP. Six different donor species are differentiated in undoped vapor phase epitaxial (VPE) layers. The two most persistent contaminants are identified with S and Si from back-doped crystals which yield useful data for uncompensated donor concentrations up to ∼5×1015 cm−3 at ∼9.5 T. The most important donor contaminant in refined halide transport VPE InP is S, but Si is dominant in layers grown with metalorganic sources of In. The TES identifications are supported by similar substructure with appropriately reduced splittings in the ionized donor BE PL. A profile of the Si/S donor concentration ratio as a function of layer thickness is presented, and the ‘‘mole-fraction’’ technique is shown to control the relative proportion of Si donors.