Comparison between GaN thin film grown by femtosecond and nanosecond pulsed laser depositions

Abstract

GaN thin films have been grown by femtosecond and nanosecond pulsed laser depositions (PLDs), respectively. X-ray diffraction, atomic force microscopy, micro-Raman spectroscopy, fluorescence spectra, scanning electronic microscope (SEM), and field emission measurements were carried out to analyze the crystalline structure, morphology, optical properties, and field emission characteristics of the deposited GaN thin films. Although GaN thin films deposited by both femtosecond and nanosecond PLD were polycrystalline and hexagonal, the crystalline quality and properties were found to be different. The SEM image of the polymer microtips array coated with GaN thin film grown by femtosecond PLD is considerably different from that of nanosecond PLD. A distortion in the shape of the polymer field emission array can be seen in the nanosecond PLD, which has been related to the differences in the laser-target interaction as well as the plume characteristics during femtosecond PLD and nanosecond PLD. The optical properties and field emission characteristics of the GaN thin film grown by femtosecond PLD are superior to the excimer laser-deposited film, suggesting that femtosecond PLD is a potential application for GaN thin films growth at low temperature.