Study of low-frequency excess noise in RTA annealed n-type gallium nitride

Low-frequency noise is investigated in n-type GaN film grown by rf-plasma assisted molecular beam epitaxy. The temperature dependence of the voltage noise power spectra, Sv(f), was examined from 400K to 80K in the frequency range between 30Hz and 100KHz, which can be modeled as the superposition of 1/f (flicker) noise G-R noise. At f > 500 Hz the noise is dominated by G-R noise with activation energies of 360meV and 65meV from the conduct band. The results clearly demonstrate the trap origin for both the 1/f noise and G-R noise. At the low-frequency range the fluctuation was dominated by 1/f noise. To determine the origin of the noise we: considered both the bulk mobility fluctuation and the trap fluctuation models. Our experimental results showed that rapid thermal annealing (RTA) at 800 degreesC resulted in over one order of magnitude decrease in the Hooge parameter. Annealing at temperatures in excess of 1000 degreesC resulted in significant increase in the noise. Photoluminescence and x-ray diffraction measurements also showed that the crystallinity of the films improved with RTA at 800 degreesC with an accompanying reduction in deep levels. Annealing at 900 degreesC and 1000 degreesC 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 the trend of Hooge paramenters as a function of annealing temperature, strongly indicating trap origin of the observed 1/f noise.