The Role Of The Space Charge Region In Surface Photovoltaic Effect

The surface photovoltage method is an important tool for semiconductor characterization. Evaluation of photocarrier diffusion length represents one of the most essential applications of this method. The technique is usually limited to samples with thick neutral bulk and thin space charge region (SCR) at the illuminated surface. The purpose of this paper is to remove these restrictions by introducing a more general model. Two different transport processes for the photogenerated carriers are assumed: drift in the SCR and diffusion in the neutral bulk. It was found that the SCR and the bulk contribute to the overall signal independently even in the case of recombination in the depletion region. The presented surface photovoltage technique was successfully applied to samples of different thickness and with differently thick space charge region at the surface. The diffusion length of the minority carrier in inorganic semiconductors as well as the diffusion length of excitons in organic materials were extracted. The thickness of the space charge region is another important parameter obtained by using the model. (C) 2014 AIP Publishing LLC.