  Due to large difference in effective masses of light and heavy holes it is
usually supposed that the above-barrier current in Schottky barriers on p-type
semiconductor is controlled only by the heavy holes. However, in real
structures, there is an additional potential barrier caused by a oxide layer at
interface. For typical values of thickness and height of a barrier its tunnel
transparency for light holes can be higher by three order of magnitude than
that for heavy holes. Due to such separative role of insulator layer one can
expect that the current is manly a contribution of light holes. To clear up
this problem the investigation of transport in a magnetic field is used as a
key experiment in this work. The pronounced magnetic field effect for heavy
holes in investigated Pb-p-HgCdTe Schottky barriers is expected only at
extremely strong magnetic fields B>10 T within the framework of both diode and
diffusion mechanism of transport. At the same time experimentally more than
twofold decrease in saturation current is observed even at B=0.5 T at any
orientation of magnetic field. The studies performed for HgCdTe with different
Kane's gap and at different temperatures show that the magnitude of magnetic
field effect is uniquely determined by the ratio of light hole cyclotron energy
to a thermal energy. However the magnitude of effect exceeds considerably the
prediction of the simple theory and the experimental magnetic field
dependencies of a saturation current do not follow the simple exponential
falling predicted for thermionic current. The reason of this discrepancy
remains a mystery.
