under high electric fields. While Franz [Z. Naturforsch. A 13, 484 (1958)] and Keldysh [Sov.
Phys. JETP 7, 788 (1958)] considered a limited case of externally applied uniform electric
field, the same effect may also be caused by built-in electric fields at semiconductor surfaces
and interfaces. While in the first case, the bands are bent linearly, in the latter case, they are
bent parabolically. This non-linear band bending poses an additional complexity that has …