SRH suppression mechanism in a non-equilibrium MWIR HgCdTe photodiode

The operation of narrow-gap semiconductor devices under non-equilibrium mode is used at temperatures where the materials are normally intrinsic. The phenomenon of minority carrier exclusion and extraction was particularly discussed in the case of the suppression of Auger thermal generation in heterojunction photodiodes, especially important in the long-wave infrared range. This paper shows that the reduction of the dark current in the HgCdTe photodiode operating in the mid-wave infrared range is primarily the result of suppression of the Shockley-Read-Hall generation in the non-equilibrium absorber. Under a reverse bias, the majority carrier concentration is held equal to the majority carrier doping level. This effect also leads to a decreased majority carrier population at the trap level and an effective increase in the carrier lifetime. The analysed device was with the following design: p+-Bp cap-barrier unit, p-type absorber doped at the level of 8 ·10¹⁵ cm¯³, and wide-bandgap N+ bottom contact layer. At room temperature, the lowest dark current density of 3.12 ·10¯¹ A/cm² was consistent with the theoretically predicted Shockley-Read-Hall suppression mechanism, about two times smaller than for the equilibrium case.