Investigation of Carrier Recombination Processes in GaAs/AlAs Multiple Quantum Wells Using Piezoelectric Photothermal and Surface Photovoltage Techniques

Abstract

We investigate the confinement, radiative, and nonradiative recombinations of photoexcited carriers in each subband of GaAs/AlAs multiple quantum wells (MQWs) using two nondestructive techniques, namely, the surface photovoltage (SPV) and the piezoelectric photothermal (PPT) techniques. In the temperature range from 160 to 300 K, there is no difference between the temperature dependences of carrier confinement in 1HH, 2HH, and 3HH subband transitions. As temperature decreased, increases in the value of the nonradiative recombination component in 2HH and 3HH were observed. These are attributed to the phonon-emitting intersubband relaxation. It was found that the number of emitted phonons by this relaxation increased with increasing order of the subband and with decreasing sample temperature. We conclude that this phonon-emitting intersubband relaxation is the most important process for electron transition in the higher-order subband in MQWs and for PPT signal generation. This is the first time that phonon-emitting intersubband relaxation was directly detected from the nonradiative recombination viewpoint.