INVESTIGATION INTO MIS STRUCTURES BASED ON GRADED-BAND-GAP HETERO-EPITAXIAL HgCdTe GROWN BY MOLECULAR-BEAM EPITAXY USING PHOTO-EMF AND CONDUCTIVITY METHODS

The effect of graded-band-gap layers on the differential resistance of space-charge region in MIS structures based on MBE HgCdTe (x = 0.225) is examined. It is shown that the effect of resistance of the epitaxial-film bulk on the measured capacitance and resistance should be taken into account for correct determination of space-charge region parameters. The presence of near-surface layers with increased Cd contents results in an increase in the resistance of the space-charge region in strong inversion. The product of semiconductor resistance by area as high as 15 Omega.cm(2) is obtained despite suppression of tunnel generation-recombination through deep levels in MIS structures with graded-band-gap layers. This might be due to background photogeneration and diffusion of minority charge carriers. The mechanisms for limitation of the differential resistance of space-charge region at different temperatures are discussed for n-HgCdTe (x = 0.225 and 0.292) and p-HgCdTe (x = 0.225).