Piezoelectric photothermal study of Al_(x)Ga_(1-x)As epitaxial layer (x=0.22, 0.28, and 0.5) grown on semi-insulating GaAs substrate

摘要

Piezoelectric photothermal measurements of an Al_(x)Ga_(1-x)As (x=0.22, 0.28, and 0.5) epitaxial layer grown on a GaAs substrate were carried out in the temperature range of 297 to 80 K. In addition to the band gap signal of the GaAs substrate, the direct transition gaps of AlGaAs were clearly observed in the higher photon energy region. It was experimentally confirmed that the temperature coefficient of the direct transition gap of Al_(x)Ga_(1-x)As alloy decreases with increasing Al mole fraction. By conducting the quenching light illumination measurements at 80 K we concluded that the photoexcited electrons in the AlGaAs epitaxial layer drifted under the influence of an electric field present at the AlGaAs/GaAs interface. The drifted electrons eventually recombined with the ionized EL2 centers in the SI GaAs substrate.