  The theory of tunnel current-voltage (I-V) characteristics of
metal-semiconductor junctions based on the self-consistent solution of Poisson
equation allows to get the Schottky-barrier height and the charged impurity
concentration directly from the tunneling data. This approach was applied to
the analysis of the low temperature experiments on tunneling under pressure up
to 3 GPa in a piston-cylinder gauge. Here we present the barrier height versus
pressure for heavily doped tunnel junctions and compare the obtained pressure
dependence of the Schottky barrier with known behavior of the band gap under
pressure taking into account the influence of the L- and X-valleys and DX
centers.
