Thickness dependence of photoluminescence excitation spectra of GaAs thin films due to confinement of excitonic polaritons

Abstract

We demonstrated a remarkable thickness dependence of the absorption caused by polariton effect of exciton in GaAs thin films. Photoluminescence excitation (PLE) spectra of high-quality GaAs films with thickness d=80–160 nm at exciton resonance were measured at low temperature (5 K). Clear peaks from quantized center-of-mass motion of exciton confined in the GaAs layer were successfully observed. We also confirm the nonlocal response of the quantized states by the observed selection rules. The thickness dependence of the absorption estimated by the PLE signal was in good agreement with the calculation results based on a transfer matrix method. These results indicate that the nonlocal response of the confined states of exciton in the layer leads to the enhancement of the internal field relevant to the confined mode of excitonic polariton.