Study of the density of states in amorphous Silicon-Hydrogen using the semiconductor/electrolyte system

Abstract

Localized states in amorphous Silicon-Hydrogen are studied by pulsed measurements on the a-Si:H/electrolyte (S/E) system. The S/E interface is essentially blocking to current flow. As a result, surface space-charge layers, ranging from large depletion to very strong accumulation conditions, can be induced and studied. Measurements in the depletion range under illumination yield directly the total density of occupied states in the entire energy gap. This is useful in obtaining a quick and reliable assessment of the quality of the amorphous films. In high grade films we find that the total density of occupied states is around 1018 cm"3. The data in the accumulation range, on the other hand, provide useful information on unoccupied states near the conduction band edge.