Electrical properties of nBn structures based on HgCdTe grown by molecular beam epitaxy on GaAs substrates

The unipolar MWIR nBn structures based on HgCdTe grown by molecular beam epitaxy on GaAs (0 1 3) substrates were created. The CdTe content in the barrier layer varied from 0.67 to 0.84 for various samples. Aluminum oxide (Al2O3) films were used to passivate the surface of the mesa structure. For fabricated samples, dark current density values were measured at various voltages in a wide temperature range. It is shown that at lower compositions in the barrier layer the dark current is limited by surface leakage. With an increase in the barrier composition, the number of structures with a bulk dark current was increased. The voltage dependences of surface and bulk current density are constructed. The activation energies for structures with the dominance of the bulk dark current are determined. It is shown that for a considerable part of structures with a large barrier composition (x = 0.84) the bulk dark current is determined by diffusion processes.