Single carrier sensing techniques in compound semiconductor detectors

For conventional radiation detectors fabricated from compound semiconductors, the wide disparity between the transport properties of the electron and holes means that detector performances are limited by the carrier with the poorest mobility–lifetime product (μτ). Finite drift lengths introduce an energy dependent depth term into the charge collection process, which effectively limit maximum detector thicknesses to a few mm for spectroscopy applications. Since mobility is a fundamental material property, the only practical way of improving μτ products is to increase carrier lifetimes, which in turn depends greatly on detector material quality and stoichiometry. Until the particular traps/defect(s) can be identified and corrected, single carrier pulse processing (e.g., rise time compensation) or sensing techniques (e.g., co-planar grids) offer the only practical means of obviating the problem. We review carrier collection in compound semiconductor radiation detectors and examine various approaches to single carrier correction and collection techniques.