Characterization of deep levels in Pt-GaN Schottky diodes deposited on intermediate-temperature buffer layers

Gallium nitride (GaN)-based Schottky junctions were fabricated by RF-plasma-assisted molecular beam epitaxy (MBE). The GaN epitaxial layers were deposited on novel double buffer layers that consist of a conventional low-temperature buffer layer (LTBL) grown at 500 degreesC and an intermediate-temperature buffer layer (ITBL) deposited at 690 degreesC. Low-frequency excess noise and deep level transient Fourier spectroscopy (DLTFS) were measured from the devices. The results demonstrate a significant reduction in the density of deep levels in the devices fabricated with the GaN films grown with an ITBL. Compared to the control sample, which was grown with just a conventional LTBL, a three-order-of-magnitude reduction in the deep levels 0.4 eV below the conduction band minimum (Ec) is observed in the bulk of the thin films using DLTFS measurements.