Reseach Of Properties Modification Of GaN Epitaxial Wafers Irradiated By Excimer Laser

In this paper, the GaN epitaxial wafers was irradiated by excimer laser. This method is a fast, economical and efficient method to improve the electrical and optical properties of GaN material and improve the LED luminecent properties.The effect of 248 nm KrF excimer laser irradiation on the properties of epitaxial wafers with a p-GaN surface were investigated. The laser irradiation-induced changes in optical and electrical properties of GaN epitaxial wafers were examined using photoluminescence(PL), I–V, XPS, SIMS and Hall test system measurements. Experimental results show that under an appropriate laser irradiated condition, optical and electrical properties of the samples were improved to different degrees. We also analyzed the effect mechanism of laser irradiation on GaN material, try to explain the process of surface modification with chemical reaction methods.To illustrate the effect of excimer laser irradiation of luminecent properties of the LED devices, we tested metal- semiconductor ohmic contact of the before and after laser irradiation samples. The results show that under an appropriate laser irradiated condition, the contact resistance decreased. The irradiated samples also had a thermal annealing treatment in different atmosphere, the results illustrate that the samples which had been annealed in oxygen had a maximum contact resistance and annealed in nitrogen had a better ohmic contact resistance. We also found that when the laser energy density of 600 mJ / cm2 or less, with the increase of the energy density of the laser irradiation, the forward current decreased, and the reverse leakage current also decreased. During the LED devices luminecent properties test, the sample annealed in nitrogen than in oxygen annealed samples showed better luminescent properties. And according to the thermal field emission theory, a brief analysis of the contact resistance and the carrier concentration of the GaN meterials as well as the Schottky barrier height oxide layer thickness was investigated, indicating that the excimer laser irradiation could improve the ohmic contact resistance.