Hydrostatic pressure effect on surface photovoltage of GaAs

Surface photovoltage phenomena: theory, experiment, and applications

“…This is because as the free carriers are generated closer to the surface, surface recombination becomes more dominant, the net excess carrier density is diminished, and the resulting SPV signal is decreased. Accordingly, SPV versus photon energy spectra have been observed to change from monotonically increasing to displaying a maximum upon, e.g., hydrostatic pressure which increased the SRV [327], or background white light which reduced the barrier height [325]. A very pronounced peak is found in the SPV spectrum corresponding to the MOCVD-grown CdTe sample in Fig.…”

“…Due to the near-E g parasitic mechanisms, it is very seldom the case that a relatively accurate value of E g can be obtained from the ®gure simply by inspection [327]. In fact, we are aware of only one such case [328].…”

“…If the samples are very thin, an interference pattern emerging in the super-bandgap region may be used for determining the thickness of the sample [295]. Based on transport considerations, Lagowski et al [327] studied À ±X valley scattering via the dependence of the SPV spectrum on hydrostatic pressure. Morawski and Lagowski [326] measured the SPV spectra of GaAs samples at liquid helium temperatures, as shown in Fig.…”

“…However, this absorption must be very strong in order to successfully compete with the response relying on the bulk density of states. Therefore, other interpretations, such as features related to, e.g., critical points in the band structure [290,327,333,358] or electron±photon interactions [326,332] must be ruled out ®rst. Finally, throughout our discussion we assume that the only effect of illumination is to induce carrier transitions.…”

Effect of Van Hove singularities on the photovoltage spectra of semiconductors

“…The direction of this transition agrees with the n-type conductivity of the sample. 29 A more moderate decrease in the CPD follows this point, which can be explained by the interplay between the increase of the DOS, as states deeper in the conduction and valence bands are made available by the increasing photon energies, and the relaxation of deep levels as the absorption depth decreases. At ϳ1.7 eV, the CPD changes from negative to positive slope ͑arrow 2͒.…”