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

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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 ($N_{\text{D}}\sim 2 \times 10^{18}$) with the lowest flat-band voltage shift (${\sim}1.6$ V) showed the least stretched $C$–$V$ curve, and the lowest effective oxide charge ($3.2 \times 10^{12}$ cm-3) and interface density ($1.2 \times 10^{12}$ 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).
2009-02-25