The subbands and resonant tunneling of a two-dimensional electron gas in a HgCdTe metal-insulator-semiconductor structure

Electron tunneling spectroscopy was performed at 77 and 4.2 K for the measurement of the tunneling current as a function of the bias voltage, which provided the information on the subbands and resonant tunneling of a two-dimensional electron gas confined in an n-type HgCdTe accumulation layer in the Hg_1-xCd_xTe-ZnS-In junction structure. Our analysis of the tunneling current versus applied bias measured at 77 K indicates that the subband energy level in a Hg_0.79Cd_0.21Te accumulation layer of a HgCdTe metal-insulator-semiconductor (MIS) structure is located at - 59 meV for the ground state and - 13 meV for the first excited state relative to the Fermi level. In addition, negative differential resistance was observed for the Hg_0.79Cd_0.21Te at 4.2 K when the applied bias was larger than the difference between the work function of Indium and the electron affinity of ZnS. Our calculation based on transfer matrix method suggests that this negative conductance be attributed to Fowler-Nordheim tunneling induced by adjusting the transmission width of a ZnS barrier.