A study of parallel-field magnetoresistance of accumulation layers at anodic oxide films on n-(Hg, Cd)Te and the diamagnetic Shubnikov-de Haas effect

Abstract

The parallel-field magnetoresistance of the accumulation layers formed at the interface between n-Hg,_,Cd,Te with x=0.2 and x=0.3 and an anodic oxide film has been studied as a function of total surface carrier density. The surface carrier density was varied using a persistent negative photoconductivity, with a lifetime in excess of hours at 77 K, caused by excitation of electrons across the anodic oxide band gap (around 3.4 eV): the electrons then recombine with ionised deep traps in the oxide. A series of strong oscillations, known as the 'diamagnetic Shubnikov-de Haas effect' (DSDH) and corresponding to the depopulation of the surface sub-bands, were observed in the parallel-field magnetoresistance. With the comprehensive data obtained in this work, and the re-interpretation of several previous results from different systems, we have been able to show that these oscillations in any accumulation-layer-type system occur at well defined fields as a function of total surface carrier density and thus that the DSDH is a remarkably 'universal' effect.

Surface Electrons in Inverted Layers of p-HgCdTe

“…Findings obtained using various magnetoresistence measurements [1][2][3][4][5][6][7] are in good agreement with data obtained from other narrow-gap non-parabolic semiconductor systems, in particular on HgTe and HgTe/CdTe superlattices [8][9][10]. It has been shown both in theory [11,12], as well as experimentally [1,5,6] that narrow-gap non parabolic materials possess common features. One characteristic of accumulation and inversion layers on such materials is a large number of occupied sub-bands, as many as five in HgCdTe [5,6].…”

“…The accuracy of the derivation may be improved by either a deconvolution of the various frequency components of the waveform, or a simulation this pattern. Summing up the S h concentration of the first three sub-bands, and adding 4% for the higher ones [5], w7e came up with the ratio of the sub-bands occupancy to total surface concentration N., presented in Table L. The concentration ratios are in excellent agreement with the theory in [12], the results of Beck and Anderson [7] and the various Singleton, Nicholas and Nasir investigations [1][2][3][4][5][6].…”

“…Seiler and Becker [14] introduced an AC technique where the magnetic field is modulated and phase sensitive detection is employed. The second derivative of the amplitude presents clear data of SdH oscillations [2,5,6,8,10]. An alternative method is using a metal-insulator-semiconductor (MIS) structure and modulating the gate voltage [1,7,15].…”

“…Summing up the S h concentration of the first three sub-bands, and adding 4% for the higher ones [5], w7e came up with the ratio of the sub-bands occupancy to total surface concentration N., presented in Table L. The concentration ratios are in excellent agreement with the theory in [12], the results of Beck and Anderson [7] and the various Singleton, Nicholas and Nasir investigations [1][2][3][4][5][6]. Taking into consideration the composition ratio (x = 0.22), our results indeed fit perfectly with a slight difference between those of x = 0.2 and x = 0.3 [2].…”

“…It has been shown both in theory [11,12], as well as experimentally [1,5,6] that narrow-gap non parabolic materials possess common features. One characteristic of accumulation and inversion layers on such materials is a large number of occupied sub-bands, as many as five in HgCdTe [5,6]. Ando [12] has shown that a large change in the band-gap energy has little effect on the relative occupancy of the various sub-bands.…”