Dielectric Passivation and Edge Effects in Planar GaN Schottky Barrier Diodes

Abstract

The influence of passivation on the edge effects (EEs) present in the capacitance-voltage (C-V ) characteristics of GaN Schottky barrier diodes (SBDs) with realistic geometry is analyzed by means of Monte Carlo simulations. The enhancement of the performance of SBDs as frequency multipliers is based on the optimization of the nonlinearity of the C-V curve, where EEs, strongly influenced by the dielectric passivation of the diode, play a significant role and must be carefully considered. The extra capacitance associated with EEs is affected by the presence of surface charges at the semiconductor/dielectric interface, which is considered by means of a self-consistent model in which the local value of the surface charge is updated according to the surrounding electron density. Our results indicate that, in realistic SBD geometries, a higher dielectric constant of the passivation material leads to more pronounced EEs. The thickness of the dielectric and the lateral extension of the epilayer are also important parameters to be taken into account when dealing with EEs.

Role of impact ionization and self-consistent tunnel injection in Schottky-barrier diodes operating under strong reverse-bias conditions

“…8,9) The use of native substrates in GaN-on-GaN SBDs allows reducing a lot of these defects, 10,11) but still a premature breakdown may take place due to the crowding of the electric field at the Schottky contact (SC) edge. 12) Extremely high values of the electric field can be found at the interface between the metal and the semiconductor, 13) which boost up the tunneling current and originate impact ionization (II) processes initiated by the tunneled electrons. 14) Local high values of the tunneling current can also be found due to inhomogeneities in the barrier height, frequently found in experiments and attributed to the poor surface quality of the GaN epilayer or to the microstructure of the metal/GaN interface.…”