High-threshold-voltage and low-leakage-current of normally-off H-diamond FET with self-aligned Zr/ZrO2 gate

Abstract

Normally-off field effect transistor (FET) is highly required for the safe and energy-efficient operation of power switching system. The hydrogen-terminated diamond (H-diamond) FET possesses outstanding properties whereas it usually shows normally on operation. In this paper, high-threshold-voltage and low-leakage-current of normally-off H-diamond FET was achieved via ZrO2/Zr gate fabricated by thermal oxidation (TO) with merits of non-pollution and simple process. The normally-off operation owed to the work function difference between Zr and H-diamond and the positive fixed charge of ZrO2. The X-ray photoelectron spectroscopy results reveal the ZrO2/Zr gate structure and the stoichiometric composition of Zr to O (1:2). The high threshold voltage (−2.7 V) and low drain-source leakage current (10−8 mA/mm) may be attributed to the Schottky barrier of Zr/H-diamond. Additionally, the gate leakage is suppressed by TO-ZrO2. The subthreshold swing, on-off current ratio and gate oxide capacitance per square centimeter are 161 mV/dec, 108 and 0.37 μF/cm2, respectively. These performances demonstrate that the ZrO2/Zr/H-diamond FET would provide an alternative approach for low power H-diamond FET.