ANALYSIS OF HIGH-FREQUENCY CAPACITANCE OF AMORPHOUS-SILICON CRYSTALLINE SILICON HETEROJUNCTIONS

High-frequency capacitance measurements as a function of applied bias of n-p amorphous-crystalline heterojunctions have been suggested as a method to evaluate band discontinuities and density of gap states in amorphous semi-conductors. However, the models used for analysing the capacitance are oversimplified and the measured capacitance data do not always follow the form predicted by these models. In this paper, we critically analyse the limitations of the existing models and present models based on a more realistic calculation of space charge in amorphous semiconductors.