The specificity of photoluminescence n-CdS/p-CdTe in semiconductor heterostructures

Abstract

The low-temperature (4.2 K) near-band-edge photoluminescence spectrum of a thin fine-grained (h, d_cr≤1μm) polycrystalline CdTe layer in an n-CdS/p-CdTe film heterostructure subjected to frontal excitation by an Ar⁺ laser with an intensity of ~44 W/cm² consists of a dominant intrinsic (e-h) emission band with a half-width Δ_A=10-12 meV and a blue shift ΔE_r » 25 meV of the red edge with respect to E_g, its LO+nLA phonon replica (Δ_B»40 meV) with a weak doublet structure, and a wide (Δ_D»100 meV) surface-interface luminescence band peaking at a frequency ħω»1.49 eV. Rear-side illumination of the photoresistive CdS layer in the intrinsic absorption range with an intensity L_{ill ≈} 5.10² lx almost completely destroys the e-hband and all related luminescence lines, which are replaced with an asymmetric polariton emission doublet having an exciton resonance frequency ħω»1.59 eV(Δ_ex» 25 meV) and a wide line of shallow donor–acceptor pairs (Δ_DAP»40 meV) at a frequency of ħω»1.54 eV, whose maximum intensity is almost two orders of magnitude lower than that of the A line in the absence of illumination.