Tunneling in tilted Si inversion layers

Abstract

The Fourier spectrum of Shubnikov---de Haas oscillations in Si metal-oxide---semiconductor field-effect transistors tilted slightly from [001] was examined. The field-sweep spectrum was found to display peaks which corresponded exactly to the combination orbits expected from electron tunneling across the minigap. The relative amplitudes of the orbits followed the variation of the size of the minigap with electron density, indicating that tunneling was a function of the size of the minigap. Digital filtering of the oscillations was used to separate the orbits, allowing each orbit to be studied individually. The data were fitted with the use of magnetic breakdown theory, and good fits were obtained. The magnetic field dependence of the amplitude of the oscillations was not dominated by breakdown effects but rather by lifetime effects. In addition, electron quantum lifetimes of various orbits were measured and found to be in good agreement with classical (magnetoconductivity) values, except for the lens which exhibited anomalously large scattering from the minigap.