Electron Tunneling and Capacitance Studies of a Quantized Surface Accumulation Layer

Abstract

This paper presents an experimental study of the effect of surface quantization in an accumulation layer on electrostatic screening. The accumulation layer exists at the InAs surface of an $n$-type InAs-oxide-Pb junction and is caused by redistribution of carriers to screen out an external electric field at the InAs surface. The results of this study confirm two predictions made by Baraff and Appelbaum. First, the appearance or disappearance of a subband of surface states introduces no sudden change in the surface potential well. Second, the magnetic quantization of the two-dimensional subbands causes oscillations in the surface potential well. We have observed the magneto-oscillations in the surface potential $U_0$ and in the $E_b$ of the quantum level, which the surface potential well supports. The oscillations in $U_0$ are observed directly in the magneto-capacitance of the junction. Moreover, these oscillations appear as a modulation to the potential barrier at the InAs-oxide interface and give rise to a new magneto-oscillatory effect in the tunneling characteristics of the InAs-oxide-Pb tunnel junctions. We have observed this new oscillatory effect and utilized it to estimate the bias dependence of $E_b$. We have also determined the effective cyclotron mass of carriers in the subband, which is approximately 10% heavier than that of carriers in the conduction band.