The `fractional thermally stimulated current' (FTSC) method: application to deep impurity levels in semi-insulating InP

Abstract

A common procedure for determining the thermal activation energies of deep levels in semiconductors is the analysis of thermally stimulated currents (TSC). The determination of activation energies from TSC measurements is afflicted with considerable uncertainties due to restricted knowledge of frequency factors, kinetics and initial occupancies of these levels. Striking examples of the deficiencies of the TSC method are given in this paper, based on computer simulations of measurement procedure and analysis. Subsequently an improved TSC technique is presented which allows us to obtain results unaffected by those uncertainties, and which gives additional insights into the underlying charge transfer processes. The potential and restrictions of this technique are illustrated by measurements on semi-insulating InP samples with different Fe concentrations.