A piezoelectric photothermal study of InGaAs/GaAs quantum well heterostructures

The optical absorption spectrum of InGaAs quantum well (QW) heterostructure samples were measured by using the piezoelectric photothermal (PPT) spectroscopy. From the room-temperature-PPT measurements and curve fitting analysis, the exciton contribution was clearly distinguished from the two-dimensional step-like band-to-band transition. Two samples of different QW structures, a molecular beam epitaxy grown single-QW (MBE-SQW) and an atomic layer epitaxy grown multiple-QW (ALE-MQW), were prepared in order to examine the availability of the PPT technique to the QW structure samples. The binding energies and FWHMs of the PPT exciton peaks were found to be 8 and 20 meV for MBE-SQW, and to be 13 and 43 meV for ALE-MQW samples, respectively. The present results show that the PPT methodology is a powerful tool for investigating the optical properties of QW structures only at room-temperature measurements