Effects of intermediate-temperature buffer layers on low-frequency noise performance of GaN based Schottky barriers

Gallium nitride based Schottky barriers were fabricated by rf-plasma assisted molecular beam epitaxy. The GaN epitaxial layers were deposited on novel double buffer layers that consisted of an intermediate-temperature buffer layer (ITBL) deposited at 690 degreesC and a conventional low temperature buffer layer grown at 500 degreesC. Low frequency excess noise was measured from the diodes. The results demonstrate clear dependency of voltage noise power spectra on the thickness of ITBL with substantial reduction in the noise level for an ITBL thickness of 800 nm. The improvement in noise performance was attributed to reduction of defect density in the GaN epitaxial layers by the utilization of ITBL in the growth process.