Peculiarities of the photon-assisted field emissions from GaN nanorods

Abstract

The peculiarities of electron field and photon-assisted field emission from GaN nanorods are presented here. Well-aligned GaN field-emitter rods with nanometer-scale diameter were processed on a wafer with n+-GaN top active layer on n+-Si substrate by plasma and photoelectrochemical etching. The current-voltage characteristics of emission current in Fowler–Nordheim (FN) plots show different slopes for the initial device and with different wavelengths illuminated devices. At electron-field emission from GaN, as a rule, the curves with two slopes (lower at a low voltage and higher at a high voltage) in Fowler–Nordheim coordinates were observed. The influence of light illumination on the field emission was discovered only on the low-voltage part of the curve. At higher voltages, the experimental curves without and with illumination practically coincided. The slope of the low-voltage part of FN plots decreased as a result of illumination. This fact points at the lowering of the energy barrier at field emission due to the electron excitation caused by light. The energy-barrier heights at field and photofield emission were estimated. For the explanation of experimental results, a model based on electron excitation by light, subbandgap and band-to-band transitions, and electron emission from different valleys with their specific electron affinities has been proposed.