Simulation of hot electron effect in negative-electron-affinity GaN pn junction diodes

A drift-diffusion device simulation model that includes energy balance equations is used for studying hot electron effect in Negative Electron Affinity (NEA) GaN pn junction diodes. Our modeling is focused on the temperature distribution of electrons prior to being emitted into vacuum where electrons have either thermalized to the lattice temperature in the band-bending region of the p-type electrode; or it is possible that some of these electrons emitted are hot. SimWindows, is used as a device modeling program for this study. We calculate electron temperature distributions and hot/cold electron density profiles in a GaN pn junction diode. Hot electron effect is modeled by Stratton's energy balance equations. A constant carrier energy lifetime is used for the electron energy loss mechanism in the interaction of electrons with lattice phonons. Our simulation results show that energy relaxation lifetime is the deciding parameter for electrons losing their energy to the lattice in the band bending region of the p-type GaN.