Magnetotransport investigations and modelling of the Hg_1-xCd_xTe-anodic oxide accumulation system

Abstract

Magnetotransport experiments on an electron accumulation system at the interface between t h e narrow-gap semiconductor cadmium mercury telluride (Hg,,Cd,Te (CMT)) and a passivating anodic oxide yield data of an extremely high quality and t h e first observation of t h e quantum Hall effect in this system. It is shown that the quality of the observed data is a result of a sharp increase in the resistivity of t h e bulk n-type CMT in a magnetic field. T h e Landau level structure of the system is calculated using a very simple scheme adapted from one originally devised for a two-dimensional system in lnSb a n d the conductivity tensor component oxx is modelled. The alternative assumptions of fixed carrier concentration and fixed Fermi energy are found to givenearly equivalent results and a good qualitative agreement with experiment is found. Estimates of the Landau level broadening parameters are made and the zerofield electron mobilities implied by these are ComDared with those deduced from cyclotron resonance measurements.

Magneto-conductance spectroscopy of a narrow-gap MIS device

“…N s = Q inv /q = (C ins /Aq) × V T , where Q inv denotes the area density of the surface inversion charge under the anodic oxide layer. The partial occupancies have been determined as 0.701, 0.222 and 0.077 of the total inversion layer carrier concentration N s and are in good agreement with the published theoretical [12,13] and experimental [9][10][11]19] values. The agreement confirms the reliability of our results.…”

“…Sweeping of V g at fixed B leads to a progressive change of not only the surface carrier concentration but consequently also of the surface electric potential well and quantized subband energies. According to theoretical [12,13] and experimental [9][10][11]19] investigations, the first excited subband is reached at the total surface carrier concentration N s ≈ 3.6 × 10 11 cm −2 , which corresponds to V g − V T = 4.6 V. The second one starts at N s ≈ 14.7 × 10 11 cm −2 which relates to V g − V T = 18.8 V. Consequently, only the first few peaks near the inversion threshold in figure 2 (between ≈ − 17 V and −12 V) represent the Landau levels in the lowest subband at 7.0 T, and within the other range of bias voltage two or three subbands are simultaneously populated. This leads to a change in periodicity of the sweep of V g and, together with the abovementioned influence on the inversion layer parameters, it complicates interpretation of the measured curves.…”

“…They measured the derivative of the capacitance with V g , dC/dV g , as a function of magnetic field strength B. Extensive studies of the Shubnikov-de Haas effect in the inversion and accumulation layers on MCT were published in [10,11]. From both types of measurement, the partial occupancy of each subband in the inversion layer can be deduced as a function of V g and of the total surface carrier concentration N s , and compared with the theoretical calculations [12,13].…”

Spin-orbit splitting in the HgTe surface quantum well

“…An alternative model is based on the assumption that the surface density is fixed. However, the two models give indistinguishable results at large enough LL broadening (this is manifested by the cosine form of the experimental oscillations) [5].…”

Quantum effects on p‐Hg1−xCdxTe (x ≈ 0.2) native surfaces

“…The 2D electron gas is produced here by the surface band bending caused by the fixed charge present in the used passivating layers. Basson and Nicholas [3] demonstrated the existence of the QHE on the electron accumulation system at the interface between n-(HgCd)Te and anodic sulphide in fields up to 14 T and at 380 mK. The analysis of results on such a system is rather complicated, as the bulk electrons are not frozen even at very low temperatures (the Fermi level lies in the conduction band).…”