LAUSR

Cadmium telluride (CdTe) thin films grown on indium antimonide (InSb) were examined by low temperature photoluminescence (PL), using an unfocused laser beam with variable excitation power over 300 times, to resolve the long standing issue of the huge variation of the resulting spectra in the deep region (1.40-1.52eV), where the expected phonon replicas alone were hardly observed. The phonon coupling strength, characterized by the Huang-Rhys parameter, or S-factor, as well as the peak width, were both found to increase with the excitation power. The puzzling coexistence of sharp peaks on top of a broad maximum was finally resolved by the awareness of beam intensity variation. Multiple phonon coupling processes can be present simultaneously, resulting in the superposition of narrow peaks on top of the broad maximum. Through the data fitting, three sets of donor-acceptor pair (DAP) recombination emissions with multiple values of Huang-Rhys parameter S can be identified.