Mobility‐trapping time &mgr;&tgr;+products of 2 × 10−4cm2/V for electrons and 3 × 10−5cm2/V for holes have been found in semi‐insulating cadmium telluride using transient response techniques. This represents a tenfold and fourfold increase in the &mgr;&tgr;+product of holes and electrons, respectively. The60Co response of surface barrier devices fabricated from this material indicates that gamma detection is possible over the extended temperature range of −100° to +100°C. Encapsulation techniques have been developed to prevent the degradation of these devices from the ambient atmosphere.