Trap-assisted tunneling in mercury cadmium telluride photodiodes

Abstract

Trap-assisted tunneling in Hg1-xCdxTe photodiodes (with x≅0.22) is modeled quantitatively. The model takes into consideration two types of deep traps: one type of energy trap is located at E t1≅40 meV (∼Eg/3) and the other type is located at Et2≅75 meV (∼2Eg/3). The density of trapped electrons at Et1∼Eg/3 is relatively high (n t1≅1014 cm-3) and is practically independent of temperature while the density of the trapped electrons at E t2≅2Eg/3 is low (nt2≅10 10-1012 cm-3) and increases with temperature. An excellent fit is systematically obtained between the calculated and measured dc dark current characteristics of typical ion implanted n+p photodiodes, in a wide range of reverse bias voltages (0