GIANT DIAMAGNETIC EFFECT IN INAS ELECTRON INVERSION-LAYERS MEASURED BY ZENER TUNNELING

Electron inversion layers on degenerate p-type InAs substrate are studied by means of Zener tunneling through the depletion layer. Two occupied subbands manifest themselves by current maxima occurring at forward biases which correspond to their minimum energies relative to the Fermi level. At magnetic fields 2.5<B<6.2 T applied parallel to the surface, in the reverse-bias range the second-derivative characteristic shows new oscillations arising from diamagnetically shifted higher subbands. In contrast to the occupied subbands, the diamagetic effect of higher subbands exceeds by a factor of 10 what is expected from the strength of the depletion field. Subband valence-band mixing and a particular form of the surface potential well are discussed as possible reasons. © 1990 The American Physical Society.