Tunneling currents in reverse biased Hg1− xCdxTe photodiodes

Abstract

A first-order, one-dimensional model for calculating bulk interband tunneling currents in reverse-biased abrupt n + p Hg 1− x Cd x Te photodiodes is presented. The tunneling probability as a function of the electron energy E is shown to be: T = exp{−√ 2m∗ h 2 √ 2ϵ 0ϵ s q 2N A E G[(1− E E G )( π 2 −sin −1√ −E E G−E )−√ −E E G ]},where E G is the bandgap, N A and ϵ S are the doping and dielectric constant of the substrate, respectively, and m∗ is the effective mass as in Kane's k·p model. The current, calculated by integrating the flux of the depletion region electrons incident on the barrier which are candidates for the tunneling process, times the tunneling probability (the value of the wavevector at the classical turning point being calculated from the non-parabolic band equation at k $ ̃ - 0) is: I A = caseq 4hπ 2 E Gk BT P 2∫ 0 −E max T( E 2 )dE,where k B is the Boltzmann's constant, P is the momentum matrix element and E max = − qV R + E; F, p − E v, p . The calculated tunneling currents are an excellent fit with measured reverse-bias current-voltage characteristics of diodes with minimized surface effects, without the need for fitting parameters.