Study of low-frequency excess noise transport in Ga-face and N-face GaN thin films grown on intermediate-temperature buffer layer by RF-MBE

We report detailed investigations of low-frequency excess noise in both Ga-faced and N-faced GaN thin films grown by RF-plasma molecular beam epitaxy. The GaN epilayers were grown on double buffer layers, and consisted of a thick intermediate-temperature buffer layer (ITBL) deposited at 690 °C and a conventional thin buffer layer. Deposition of the thin buffer layer is used to control the polarity of the GaN epilayer. Low-frequency excess noise was studied in detail to examine the effects on the ITBL on the noise. The low-frequency noise is attributed to the correlated fluctuations in number and mobility of carriers, arising from the capture and emission by localized states. Our experimental results show that the polarity of the GaN epilayer and the utilization of ITBL have strong influence on the defect density of the GaN material.