Derivative surface photovoltage spectroscopy; a new approach to the study of absorption in semiconductors: GaAs

Abstract
Derivative surface photovoltage spectroscopy was achieved with wavelength modulation; it was applied to GaAs and permitted, in a single experiment, the determination of changes in the absorption coefficient over an energy range of 0.5 to 4.3 eV. Photoionization characteristics of deep levels were determined. All known critical‐point transitions up to 4.3 eV were clearly obtained from second‐derivative spectra. In addition, previously unresolved transitions were observed at about 2.6 eV. Oscillatory photovoltage in high magnetic fields was observed, and it was used to identify the transitions in the vicinity of the energy gap.