Superlattice Barrier HgCdTe nBn Infrared Photodetectors: Validation of the Effective Mass Approximation

Abstract

Implementation of the unipolar barrier detector concept in HgCdTe-based compound semiconductor alloys is a challenging problem, primarily because practical lattice-matched materials that can be employed as the wide bandgap barrier layer in HgCdTe nBn structures present a significant valence band offset at the n-type/barrier interface, thus impeding the free flow of photogenerated minority carriers. However, it is possible to minimize the valence band offset by replacing the bulk HgCdTe alloy-based barrier with a CdTe-HgTe superlattice barrier structure. In this paper, an 8 × 8 k.p Hamiltonian combined with the nonequilibrium Green's function formalism has been employed to numerically demonstrate that the single-band effective mass approximation is an adequate numerical approach, which is valid for the modeling, design, and optimization of band alignment and carrier transport in HgCdTe-based nBn detectors incorporating a wide bandgap superlattice barrier.Index Terms-8 × 8 k.p, infrared (IR), mercury cadmium telluride (HgCdTe), nBn detector, nonequilibrium Green's function (NEGF), numerical simulation, unipolar barrier.

Quantum simulations of band-to-band tunnelling in a type-II broken-gap superlattice diode

“…It became possible (and necessary) due to (i) adaptation of the complex formalism into 'easy to implement' equations [9], (ii) intense growth of computational resources and development of numerical algorithms, both enabling the efficient use of the method, (iii) development of new devices whose operation relies on quantum phenomena. Consequently, in recent years, the NEGF method has been used for studying electronic transport phenomena in resonant tunnelling diodes [10], field effect [11] and tunnelling [12] transistors, carbon nanotube devices [13], light-emitting diodes [14][15][16], photodetectors [17][18][19], quantum-well solar cells [20][21][22], quantum [23][24][25][26] and inter-band [27] cascade lasers and, eventually, SL-based devices [28][29][30][31].…”