Microstructural and interface properties of Au/SrTiO3 (STO)/n-GaN heterojunction with an e-beam evaporated high-k STO interlayer

Abstract

This paper reviews the microstructural and electrical properties of Au/n-GaN metal/semiconductor (MS) diode with an e-beam evaporated SrTiO3(STO) as an insulating layer between the Au and n-GaN substrate. The microstructural properties of STO thin films are assessed by employing XRD and TEM approaches and the results reveal that the STO thin films are formed on n-GaN surface. Then, the Au/STO/n-GaN heterojunction (HJ) type Schottky diode is fabricated and measured its electrical characteristics by current-voltage (I–V) and capacitance-voltage (C–V) techniques. The HJ exhibits lower reverse leakage current compared to the MS diode. Higher barrier height is achieved for the HJ (0.86 eV) than the MS diode (0.67 eV) with ideality factors of 1.86 and 1.21. This implies that the barrier height is modified by the STO insulating layer. Using Z(V,T)i - Vd and ΨS-V plots, the barrier heights of MS diode and HJ are also evaluated and compared with one another. The derived interface state density (NSS) of HJ is lower than the MS diode, demonstrating that the STO layer plays a substantial role in the reduced NSS. Results suggest that the STO thin film is a promising high-k material for the development of new electronic device applications.