  A new method of self-consistent quantum calculation of the density of the
space charge near the surface of a crystal is carried out for the semiconductor
with nonparabolic (Kane) dispersion law of bands. The remarkable feature is the
solution of the Schroedinger equation for electrons and holes in the energy
range, including both bound energy states and states in the continuum.
Theoretical voltage-capacitance dependence is calculated and coincides with
experimental data. The dependence of the electron mass and surface mobility
from the value of surface potential are analyzed.
