Unipolar superlattice structures based on MBE HgCdTe for infrared detection

Mid-wave infrared nBn structures based on HgCdTe grown by molecular beam epitaxy on GaAs (013) substrates were fabricated. A wide-gap Hg 1- x Cd x Te ( x = 0.75 and 0.84) and a superlattice of 18 periods Hg 0.20 Cd 0.80 Te (9 nm)–HgTe (2 nm) were used as a barrier layer. In a wide temperature range, the mechanisms of the formation of dark current–voltage characteristics of fabricated nBn structures were studied. It was shown that for a barrier with a composition of 0.75, surface leakage currents dominate, and for a barrier with a composition of 0.84, the bulk component of the dark current dominates. For superlattice structures, the bulk current value is greater than for the wide-gap barrier, which is associated with a decrease in the height of the potential barrier for holes. The admittance of metal–insulator-semiconductor (MIS) test systems based on superlattice structures was studied. The features of the capacitance–voltage characteristics of MIS capacitors based on the superlattice nBn structure associated with changes in the differential resistance of the barrier layer at different polarity of the bias voltage are revealed.