Surface photovoltage spectroscopy in infra-red and visible range for p-type CdTe

Surface photovoltage phenomena: theory, experiment, and applications

“…The observation of both transitions indicates a partial ®lling of the state involved, and hence non-equilibrium conditions. Similar effects have also been encountered by other groups [386,393,397]. Goldstein and Szostak measured a-Si:H samples at low temperatures [303].…”

“…47 were identi®ed as bulk and surface phonons, respectively, using a similar comparison with photoconductivity. More examples of use of this procedure may be found in, e.g., [319,334,360,365,366,371,375,386,407].…”

“…Increasing the band-bending via an external dc bias in a MIS arrangement also improves the SNR. A different approach relies on lowering the measurement temperature [298,386], which suppresses thermally-induced transitions and hence increases both the super-and sub-bandgap SPV (see Section 2). An example is shown in Fig.…”

“…When long response-time transitions are involved, their corresponding SPV features are likely to go undetected when using ac SPV because the illumination chopping rate may be too fast to allow any non-negligible population changes in the`slow' states involved [100,110,321,386]. In fact, Gatos et al [6] have been able to advance SPS much more than other early researchers [100,239] partly because they used dc, rather than ac, spectroscopy, thereby revealing a set of surface states not previously exposed.…”

“…The lack of sensitivity of ac SPV to slow states has also been used bene®cially. The presence of some spectral features in dc, but not ac, SPV, has been used to conclude that the observed features are related to surface, rather than bulk, states [6,386,393,394]. While this method has been used with some success, it is in fact quite limited because it assumes that bulk states are invariably fast and surface states are invariably slow, which is not always true.…”