Modified Interface Properties of Au/n-type GaN Schottky Junction with a High-k Ba0.6Sr0.4TiO3 Insulating Layer

Abstract

The interface properties of a Au/n-GaN Schottky junction (SJ) were modified by placing a high-k barium strontium titanate (Ba0.6Sr0.4TiO3) insulating layer between the Au and n-GaN semiconductor. The surface morphology, chemical composition, and electrical properties of Au/Ba0.6Sr0.4TiO3 (BST)/n-GaN metal/insulator/semiconductor (MIS) junctions were explored by atomic force microscopy, energy-dispersive x-ray spectroscopy, current–voltage (I–V) and capacitance–voltage (C–V) techniques. The electrical results of the MIS junction are correlated with the SJ and discussed further. The MIS junction exhibited an exquisite rectifying nature compared to the SJ. An average barrier height (BH) and ideality factors were extracted to be 0.77 eV, 1.62 eV and 0.92 eV, 1.95 for the SJ and MIS junction, respectively. The barrier was raised by 150 meV for the MIS junction compared to the MS junction, implying that the BH was effectively altered by the BST insulating layer. The BH values extracted by I–V, Cheung’s and Norde functions were nearly equal to one another, indicating that the techniques applied here were dependable and suitable. The frequency-dependent properties of the SJ and MIS junction were explored and discussed. It was found that the interface state density of the MIS junction was smaller than the SJ. This implies that the BST layer plays an imperative role in the decreased NSS. Poole–Frenkel emission was the prevailed current conduction mechanism in the reverse-bias of both the SJ and MIS junction.