An excess tunnel current in GaP epitaxial nondegenerate p-n junctions on Ga
P and Si substrates was studied. An important experimental result is that t
he slope of exponential current-voltage (I-V) characteristic (in lnI-V coor
dinates) is independent of the width of the space-charge region, i.e., on n
- and p-region doping levels. This fact is unexplained by existing models.
A dislocation shunt model based on multihop tunneling through a dislocation
line, which may be considered as a chain of parabolic potential barriers,
is proposed. The density of dislocations predicted by this model is in agre
ement with the transmission electron microscopy (TEM) observations. (C) 200
0 MAIK "Nauka /Interperiodica".