Investigation of the annealing effect on the nonradiative carrier recombination in AlGaAs/GaAs utilizing the piezoelectric photothermal technique

The electron nonradiative recombination process of photoexcited carriers in as-grown and annealed n= Al 0.2 Ga 0.8 As/GaAs heterostructure samples is investigated by using piezoelectric photothermal (PPT) spectroscopy. The PPT signal above the band-gap energy of GaAs substrate decreased when the sample was annealed at 815 °C. In the frequency dependent measurements, the deviations from the 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 the AlGaAs epitaxial layer region and this level effectively traps the photoexcited carriers nonradiatively.