Surface passivation of HgCdTe photodiodes

Abstract

At higher temperatures HgCdTe photodiode dark currents are usually limited by bulk material properties exhibited as diffusion currents. As the temperature is decreased diode the dark currents transition to a region of smaller temperature dependence consistent with generation recombination in the space charge region, whereas at yet lower temperatures diode dark currents are limited by interband tunneling. The latter two effects are often of a surface origin. Two classes of surface passivation insulators are discussed: (1) the classical dielectric insulator in which the space charge width far exceeds the insulator thickness; and (2) the heterostructure passivation in which doping and/or thickness of the ‘‘insulator’’ are high enough for space charge layers and associated barriers to fully develop.