Admittance of barrier nanostructures based on MBE HgCdTe

Abstract

Mid- and long-wave infrared nBn structures based on HgCdTe grown by molecular beam epitaxy (MBE) on GaAs (013) substrates were fabricated. For mid-wave nBn structures, the composition in the absorbing layer was 0.29, and for long-wave nBn structures, this composition was 0.21. The composition in the MBE HgCdTe barrier layers ranged from 0.61 to 0.67. Based on the fabricated HgCdTe nBn structures, test metal–insulator–semiconductor (MIS) devices were created by applying a dielectric Al2O3 film with the thickness of about 90 nm. The admittance of test MIS devices was investigated over a wide range of frequencies and temperatures. An equivalent circuit of MIS device based on MBE HgCdTe nBn structure is proposed, which includes the dielectric capacitance, the capacitance and resistance of the barrier layer, and the series resistance of the absorbing layer bulk. It is shown that the values of the equivalent circuit elements are easy to determine from the experimental frequency dependences of admittance in accumulation mode. Comparison of element values for MIS devices based on mid-wave and long-wave nBn structures is carried out.