Electronic field-assisted emission from GaN: the role of surface charges

A finite-difference model for computing the band diagram and diode current of biased metal-semiconductor-metal systems is presented. The open-boundary conditions that enable the modeling of metal-semiconductor-vacuum configurations, in which the driving force is the electric field in the vacuum is also introduced. This model includes an exact calculation of the emission current through the surface barrier. In particular, the screening effect of surface charges and how the band diagram of the semiconductor is affected by the emission current are considered and studied. This study focuses on n-doped GaN layers.