Electrical Properties of Al/HfO2/n-GaN Prepared by Reactive Sputtering Method

Abstract

In this study, the effects of the doping concentration of n-type GaN on Al/HfO2/GaN metal–oxide–semiconductor capacitors that incorporated sputtered HfO2 gate dielectric were determined. Electron mobility decreased and conductivity increased as doping concentration increased. The FWHM of the X-ray rocking curves of GaN(0002) also increased with doping concentration. A positively shifted and stretched capacitor–voltage (C–V) curve relative to the ideal one was obtained. Accumulation capacitance increased slightly as doping concentration increased, increasing the dielectric constant and effective oxide thickness. A moderately doped sample (ND∼2 ×1018) with the lowest flat-band voltage shift (∼1.6 V) showed the least stretched C–V curve, and the lowest effective oxide charge (3.2 ×1012 cm-3) and interface density (1.2 ×1012 cm-2) among the studied samples. Results of this study significantly contribute to the development of GaN-based metal–oxide–semiconductor field-effect transistors (MOSFETs) or metal–oxide–semiconductor heterojunction field-effect transistors (MOSHFETs).