Space-charge analysis for the admittance of semiconductor junctions with deep impurity levels

The space charge analysis within depletion layers in semiconductors containing deep trap levels is reconsidered. A simple approach to the frequency dependence of the admittance ofp⁺/n junctions is properly generalized in order to deal with the effect of interface states at heterojunctions and Schottky barriers, as well as with a special case for the space distribution of the trap density. The density of interface states atp-Ge/CdS heterojunctions is so derived. Approximate analytical solutions accounting for a spatially distributed time constant are obtained for the admittance ofp⁺/n junctions with a single trap state. A comparison with experimental data is given and discussed.