Enhanced numerical modelling of non-cooled long-wavelength multi-junction (Cd,Hg)Te photodiodes

The theoretical analysis of long wavelength uncooled photovoltaic devices based on complex two-dimensional Hg_1-xCd_xTe heterostructures is presented. An enhanced computer program has been developed to solve the system of nonlinear continuity equations and the Poisson equation. All physical quantities of semiconductor structure are expressed as functions of electric potential and Fermi quasi-levels. The noise analysis is based on the set of ´transport equations for fluctuations´ that enables calculations of spatial distribution of electrical potential and Fermi quasilevel fluctuations. Both generation recombination noise and If noise caused by mobility fluctuations were taken into account. The results of calculations are presented as maps illustrating spatial distributions of current densities, electrical gain, and fluctuations of selected physical quantities. Detectivity of 4×10⁷ cmHz¹2/W^-1 is predicted for a 10.6 μm unbiased multiple heterojunction photovoltaic device with 20 μm period. The theoretical predictions have been compared with performance of practical devices.