Finite element calculations were made of the expected potential profile around negatively charged threading dislocations close to a metal/semiconductor interface, using a Pt contact on a n-type GaN as a specific case. The potential was calculated as a function of the assumed linear density and energy level of threading dislocation-related acceptors. The model showed good agreement with the 1954 model of Read for an infinite dislocation far from any interface. Assuming 1 acceptor/c-axis lattice spacing (c = 0.52nm), it was found for near-surface modeling that acceptors levels deeper than 1.3eV below the conduction band minimum should be charged all the way to the Pt/GaN interface. This was expected to produce a significant local increase in the potential barrier and, at the Pt/GaN interface, to be observable via ballistic electron emission microscopy. Recent ballistic electron emission microscopic measurements of molecular beam epitaxially grown GaN films had shown no significantly increased barrier at threading dislocations; thus indicating an acceptor energy within 1.3eV of the conduction band minimum and/or an acceptor density of less then 1 acceptor/c-axis lattice spacing.

Calculated Potential Profile near Charged Threading Dislocations at Metal/Semiconductor Interfaces. C.Tivarus, Y.Ding, J.P.Pelz: Journal of Applied Physics, 2002, 92[10], 6010-3