Spectroscopic observation of D −, D° and cyclotron resonance lines in n-GaAs and n-InP at intermediate and strong magnetic fields and under different conditions of bias, temperature and pressure

Abstract

Spectroscopic transitions originating from D - states in n-GaAs and n-InP are investigated under a variety of experimental conditions of illumination, temperature, bias field and pressure and are compared with D° transitions and cyclotron resonance lines. When the magnetic field parameter γ exceeds unity a considerable divergence between experimental and theoretical values of binding energy for the D - ground state is found indicating the inadequacy of existing variational calculations. Increasing the electric field applied to the sample is found to strongly enhance the D - occupancy and this is explained in terms of the cross- sections for ionisation and recombination of the D - and D° centres. Hydrostatic pressure is found to enhance strongly the D - lines in InP but not in vpe GaAs. This is explained in terms of a change in effective compensation of the shallow donors in vpe GaAs produced by a level- crossing with donor states associated with higher conduction bands. This does not occur for InP in the pressure range available and the increase in D - intensity is thought to arise from the reduction in extent of the wavefunctions.