Effects of rapid thermal annealing (RTA) on the structural properties were investigated in undoped GaN film grown by rf-plasma-assisted molecular beam epitaxy (MBE). Detailed characterizations of the photoluminescence (PL), high-resolution X-ray diffraction and low-frequency noise were conducted on both the as-grown and annealed films. PL and X-ray diffraction measurements showed that the crystallinity of the films improved with RTA at 800 °C with significant reduction in the yellow emission. Annealing at 900 °C and 1000 °C resulted in an increase in the FWHM of the X-ray diffraction, indicative of thermal decomposition of the materials. The results are in excellent agreement with our study of low-frequency noise, which demonstrates similar trend in the magnitudes of the Hooge parameters as a function of the annealing temperature. The temperature dependence of the voltage noise power spectra Sv (f) was examined from 400 K to 80 K in the frequency range between 30 Hz and 100 kHz. At the low-frequency range the fluctuation is dominated by 1/fγ noise, and for f > 1 kHz the noise is dominated by G-R noise processes. Our experimental results show that 800 °C is the optimal temperature for RTA, which results in substantial improvements in both the optical, structural and noise properties for the material, whereas annealing at 1000 °C is found to result in significant material degradation.
- Gallium nitride
- Low-frequency noise
- Rapid thermal annealing (RTA)
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering