Effect of the Photoquenching of EL2 in GaAs Substrate on the Piezoelectric Photothermal and Surface Photovoltage Spectra of a GaAs Single Quantum Well Confined by GaAs/AlAs Short-Period Superlattices

Abstract

Two nondestructive techniques, surface photovoltage (SPV) and piezoelectric photothermal (PPT) spectroscopies, were adopted to investigate a GaAs single quantum well (SQW) confined by GaAs/AlAs short-period superlattices (SPSs) fabricated on a semi-insulating (SI) GaAs substrate, whose absorption spectra cannot be obtained easily using conventional techniques. Excitonic absorptions associated with subband transitions in a GaAs SQW and SPSs were clearly observed. We also examined how a SI-GaAs substrate affects the PPT and SPV spectra, particularly the effect of the photoquenching of the deep donor level EL2. It was found that the photoquenching of EL2 causes a significant change in the total built-in potential at the interface between the epitaxial layers and the substrate, and affected the signal intensities observed in the PPT and SPV spectra. The present experimental results have shown that a large amount of carrier leakage occurs from a GaAs SQW and SPSs to the sample surface, even in the presence of Al0.3Ga0.7As buffer layers.