Photothermal wavelength modulated photocurrent phenomena in Si delta-doped GaAs

The first observation of photothermal wavelength modulated photocurrent (PWMPC) phenomena in a MBE grown p-GaAs sample in which a single Si-layer was embedded with a delta-type profile, is reported. Two spectral features were observed at 1.5137 eV and 1.5115 eV at 20 K. These peaks were attributed to the (D-0, X) and (A(0), X)-excitons bound to neutral donors and accepters respectively. We studied the temperature dependence of these excitonic peak positions at temperatures between 20-90 K. Additionally, we demonstrate a blue shift of spectra under low level illumination intensity. PWMPC phenomena and the nature of the registered features were explored in detail. The dependence of the excitonic peaks on the chopping frequency and the intensity is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.