Electrical Characteristics of H-Diamond Transistors With ZrO₂/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 ZrO2/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 <tex-math notation="LaTeX">8~μ m </tex-math> , indicating the normally- OFF operation. The OFF-state leakage current of 10−8 mA/mm and gate–source leakage current density of about <tex-math notation="LaTeX">10^-7 </tex-math> A/cm2 were acquired both for 6- and 8- <tex-math notation="LaTeX">μ m </tex-math> gate length devices. Additionally, the ON/OFF ratio and subthreshold swing (SS) for the device with a 6- <tex-math notation="LaTeX">μ m </tex-math> gate length were deduced to be <tex-math notation="LaTeX">10^9 </tex-math> 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- <tex-math notation="LaTeX">μ m </tex-math> gate length. These performances suggest that the EB method is applicable to fabricate the ZrO2/Zr gate for realizing normally- OFF H-diamond FETs.