The dislocation origin and model of excess tunnel current in GaP <i>p-n</i> structures

An excess tunnel current in GaP epitaxial nondegenerate p-n junctions on GaP and Si substrates was studied. An important experimental result is that the slope of exponential current-voltage ( I–V ) characteristic (in ln I–V coordinates) 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 agreement with the transmission electron microscopy (TEM) observations.