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 Et1≂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 (nt1≂1014 cm−3) and is practically independent of temperature while the density of the trapped electrons at Et2≂2Eg/3 is low (nt2≂1010–1012 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<Vd<−1.5 V) and operating temperatures (30–120 K).

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