Novel HgxCd1−xTe device structure for higher operating temperature detectors

Abstract

A novel detector structure in which photons are absorbed in narrow-gap material, but the junction lies in wider bandgap material, has been examined. A possible reduction in bulk 1/f noise by a factor of 33 for a 240 K operation was predicted, based on studies that have suggested that the source of 1/f noise is the p-n junction and the large reduction in 1/f noise, which is observed in conventional detectors when the bandgap is increased. The increased bandgap at the junction produces a potential barrier; however, calculations are presented showing that for T > 150 K the thermal energy of the electrons enables them to cross the barrier and reach the p-n junction before recombining in the active region, thus giving high quantum efficiency. Experiments performed on the diodes showed that the quantum efficiency was maintained as expected, but the 1/f noise was not reduced, suggesting that it does not originate at the p-n junction. However, the structure does give excellent reverse-bias characteristics with low breakdown even at 2-V reverse bias.