Impact of laser wavelength on pulsed laser deposition method-deployed gallium nitride (GaN) thin films

Abstract

Pulse laser deposition (PLD) was used to produce and deposit nanofilms of gallium nitride (GaN) with a nanocrystalline structure on quartz substrates. The pulsed laser wavelength effect on the structural and optical properties of these films was studied. The PLD process achieved with the constant parameters includes a temperature of 300°C, a frequency of 3 Hz, a number of pulses of 250, and a voltage of 900 V, but with the three various wavelengths of the pulsed laser, it includes 1.064, 0.532, and 0.355 μm. The influence of varying deposition conditions, such as laser wavelengths (1.064, 0.532, and 0.355 μm), on the optical and structural characteristics of these nanofilms was examined. The characteristics were examined utilizing several analytical techniques, including X-ray diffraction (XRD) and UV-Visible spectrophotometry (UV-VIS). The XRD results indicated that the crystalline structure of the deposited films enhances with an increase in laser wavelength, laser energy, substrate temperature, and the use of a target with an equal material ratio, as evidenced by the heightened peak intensity. The ultraviolet-visible (UV-vis) was used to characterize and study these nanostructure thin films. According to the UV-vis measurements, the refractive index achieved the same values when wavelengths of the pulsed laser, 1.064 µm and 0.532 µm, were used. As the wavelength of the pulsed laser increases, the values of absorption also increase, while the optical energy gap values decrease, but the transmission values exhibit random behavior with this increase. So, from these results, we can find the two various laser wavelengths (1.064 µm and 0.532 µm) achieved very similar results except for the transmission results, which means that using any one of them in the deposition process will achieve the same results for the desired application.