Electrical Characteristics of H-Diamond Transistors With ZrO $_{\text{2}}$ /Zr Stacked Dielectrics Deposited by Electron Beam Evaporation

Enhancement mode diamond field-effect transistors with large threshold voltage and low leakage current are highly in demand for low-power electronics. In this article, hydrogen-terminated diamond (H-diamond) transistors with ZrO $_{\text{2}}$ /Zr stacked dielectrics deposited by electron beam (EB) evaporation were demonstrated. The threshold voltages boosted from $-$ 0.4 to $-$ 2.5 V with gate length increasing from 2 to 8 $\mu $ m, indicating the normally-OFF operation. The OFF-state leakage current of 10 $^{-\text{8}}$ mA/mm and gate–source leakage current density of about 10 $^{-\text{7}}$ A/cm $^{\text{2}}$ were acquired both for 6-and 8- $\mu $ m gate length devices. Additionally, the ON/OFF ratio and subthreshold swing ( SS ) for the device with a 6- $\mu $ m gate length were deduced to be 10 $^{\text{9}}$ and 128 mV/decade, respectively. The maximum drain current density increases with the gate length shortens and reaches up to $-$ 74 mA/mm for the device with a 2- $\mu $ m gate length. These performances suggest that the EB method is applicable to fabricate the ZrO $_{\text{2}}$ /Zr gate for realizing normally-OFF H-diamond FETs.