Low-frequency excess noise was measured from GaN thin films deposited by plasma assisted molecular beam epitaxy (MBE). The noise power spectra is dominated by 1/f noise at low frequency and by Lorentzians at frequencies beyond 3 kHz. The temperature dependencies of the Lorentzians were examined from room temperature to about 90 K. From the Arrhenius plot of the time constants, the thermal activation energy of the fluctuation time constant was found to be around 30 meV. From the temperature dependencies of voltage noise power spectra, we estimated the magnitudes of the capture and emission activation energies. Based on the results, we have formulated a model, which stipulates that the generation-recombination (G-R) noise arises from the capture and emission of carriers by localized states in the bulk of the film. The process leads to fluctuations in the carrier mobility due to the modulation of the Coulombic scattering rate. We next conducted a systematic investigation on the effects of rapid thermal annealing on G-R noise in GaN thin films. Experimental results showed that annealing at 900°C resulted in the minimum FWHM in the rocking curve. Furthermore, we observed a substantial reduction in the noise level, indicating that rapid thermal annealing can be used as an effective means for noise reduction in GaN based devices.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Condensed Matter Physics
- Safety, Risk, Reliability and Quality
- Surfaces, Coatings and Films
- Electrical and Electronic Engineering