Annealing Effect on the Nonradiative Carrier Recombination in AlGaAs/ GaAs Investigated by a Piezoelectric Photothermal Spectroscopy.

摘要

Electron non-radiative recombination process of photoexcited carriers in as-grown and annealed n-Al0.2Ga0.8As/GaAs hetero-structure samples are investigated by using a piezoelectric photothermal spectroscopy (PPTS). The PPT signal above the band-gap energy of GaAs substrate decreased when the sample was annealed at 815 deg C. In the frequency dependent measurements, the deviations from 1/f linear function are clearly observed in the AlGaAs/GaAs samples. This critical deviation frequency was found to shift to the lower frequency region by annealing. Our experimental results are explained by assuming that the sample annealing generates an unknown deep level in AlGaAs epitaxial layer region and this level effectively traps the photoexcited carriers non-radiatively.