Thermally Stimulated Currents in Semiconductors and Insulators Having Arbitrary Trap Distributions

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Abstract
The theory is developed for thermally stimulated currents (TSC) that flow in optically or electrically excited insulators and semiconductors in which the field is sufficiently high and the (active) region in which the free carriers are generated is sufficiently thin (e.g., reverse-biased junctions, thin films, etc.) so that recombination rate of the free carriers is negligible. Closed-form solutions are obtained for the TSC characteristics for semiconductors and insulators containing arbitrary trap distributions. Using various ad hoc trapping distributions, it is shown that the approximate high-field TSC characteristics correlate extremely well with the exact characteristics that were computed numerically. More important, however, it is shown that the shape of the observed TSC characteristic is a direct reflection of the sum of the trap distribution in the upper half and the lower half of the band gap. The technique is potentially a powerful means of characterizing trap distributions in defect semiconductors and insulators, in that it permits the direct determination of the trap distribution without requiring an a priori knowledge of the trap parameters and without the need for laborious analyses.