Enhancement-mode hydrogenated diamond metal-oxide-semiconductor field-effect transistors with Y₂O₃ oxide insulator grown by electron beam evaporator

Enhancement-mode (E-mode) hydrogenated diamond (H-diamond) metal-oxide-semiconductor field-effect transistors (MOSFETs) are fabricated with an Y₂O₃ oxide insulator grown on the H-diamond directly using an electron beam evaporator. The depletion region of the capacitance-voltage curve for the MOS capacitor shifts to the left hand side relative to 0 V, which indicates the existence of positive charges in the Y₂O₃ film. There are distinct pinch-off and p-type channel characteristics of the Y₂O₃/H-diamond MOSFETs. The maximum drain-source current for the MOSFET without interspace between the source/drain and the gate (L_S/D-G) is −114.6 mA mm⁻¹. Those for the MOSFETs with L_S/D-G are decreased from −11.0 to −2.1 mA mm⁻¹ with the gate length increasing from 3.3 ± 0.1 to 15.4 ± 0.1 μm. Threshold voltages for all the MOSFETs are negative, indicating their E-mode characteristics. Negatively charged adsorbates are one of the necessary conditions for hole accumulation of the H-diamond channel layer, which are possibly compensated by the positive charges in the Y₂O₃ film, resulting in E-mode characteristics of the MOSFETs.