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

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.