Investigation On The Propertites Of GaN Layer Irradiated By High-energy Electron

Gallium nitride (GaN) exhibits some unique properties, such as a large direct band gap,strong interatomic bonds, and a high thermal conductivity, which make it an ideal material foroptoelectronics, high-temperature/high-power devices and short wavelength devices. In someapplications, such as nuclear technology and satellite communication, GaN-based componentshave to stay operable when subjected to high doses of ionizing radiation. It is therefore importantto study the effect of irradiation on the electrical and optical properties of semiconductor materialand to study the diffusion and annihilation of the irradiation defects in the rapid thermalannealing treatment.In this paper, GaN layer irradiated by high-energy electron was investigated by means ofdouble crystal X-ray diffraction (DCXRD), positron annihilation spectra (PAS), scanningelectron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL)spectra and Hall measurement. The main results are summarized as follows:1. The irradiated defects in the electron-irradiated GaN layer were studied by the method ofwet chemical etching, the electron-irradiated GaN layer was etched by the melt KOH andNaOH solutions, the SEM result shows that three kinds of etching pit are observed which isthe same as the etching pit of dislocation, therefore, it is proposed that the irradiated defectshave the similar characteristic with the dislocation.2. The effect of electron irradiation on the yellow luminescence was studied, a theoreticalmodel was first proposed to interpret the relation between the yellow luminescence intensityand the irradiation dose. The concentration of Ga vacancy introduced by electron irradiationincreases with the irradiation dose, Ga vacancy is associated with the origin of yellowluminescence, thus, the intensity of yellow luminescence increase with the irradiation dose.3. The effect of rapid thermal annealing on the yellow luminescence was studied, the resultshows a non-linear dependence on the annealing temperature up to800oC. The thermalactivation energy of yellow luminescence for the400oC-annealed sample is16meV, which isrelated to oxygen; the thermal activation energy of yellow luminescence for the600oC-annealed sample is40meV, which is associated with carbon. In view of the diffusion of the irradiated defects, it is proposed that two mechanisms of the yellow lumiscence areinvolved in the whole annealing process.4. The effect of electron irradiation on electrical parameters in GaN layers was studied, atheoretical model was first proposed to interpret the relation between the electricalparameters and the irradiation dose. The concentration of deep level introduced by electronirradiation increases with the irradiation dose, the decrease of the carrier concentration andmobility is caused by the trapping and scattering of the carrier.5. The effect of rapid thermal annealing on electrical parameters in GaN layers was studied, theresult shows that the carrier concentration and mobility show a non-monotonous dependenceon the annealing temperature up to800℃. The carrier concentration and mobility in theannealing range200~600℃are attributed to the combination and dissociation of Ga vacancyacceptor and O shallow donor, the carrier concentration and mobility at the annealingtemperature of800℃are associated with N vacancy shallow donor.