Magnetocapacitance measurements of subband separation in an accumulation layer on n - Type GaAs

Abstract

Magnetocapacitance measurements on an n - type GaAs undoped AlxGa1-xAs/n+-type GaAs (AlGaAs) capacitor are used to determine the subband separation E1-E0 for an accumulation layer on n - type GaAs. For values of surface electron concentration NS large enough that two subbands can be occupied, and for certain values of magnetic field, B, Landau levels in the lowest subband coincide with those in the first excited subband. The result is a characteristic sequence of maxima in the density of states at the Fermi level which is detected as a sequence of maxima in magnetocapacitance curves of an AlGaAs capacitor. For the sample studied, E1-E0 varies between 24.5 and 33.5 meV for 8.9×1011<NS<13.1×1011, somewhat less than calculated values. © 1989 The American Physical Society.