Abstract
Two nondestructive techniques of surface photovoltage (SPV) and piezoelectric photothermal (PPT) spectroscopies were adopted to investigate GaAs/AlAs multiple quantum well (MQW) heterostructures fabricated on a GaAs substrate, which is difficult to obtain the absorption spectra using a conventional technique. Excitonic and two-dimensional step-like subband absorptions corresponding to the density of states of MQW were obtained by subtracting the background signal from the substrate signal at room temperature. We also conclude that a difference between SPV and PPT spectra indicates the nonradiative component of the carrier relaxation processes in MQW. We found that the combination of SPV and PPT measurements is a powerful method of investigating the carrier confinement and recombination processes in MQW.
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