Performance of normally off hydrogen-terminated diamond field-effect transistor with Al₂O₃/CeB₆ gate materials

In this work, we demonstrate a hydrogen-terminated diamond (H-diamond) field-effect transistor (FET) with Al₂O₃/CeB₆ gate materials. The CeB₆ and Al₂O₃ films have been deposited by electron beam evaporation technique, sequentially. For the 4/8/12/15 μm gate length (L_G) devices, the whole devices demonstrate distinct p-type normally off characteristics, and all the threshold voltage are negative; all the absolute values of leakage current density are 10⁻⁴ A/cm² at a V_GS of −11 V, exhibiting a relatively low leakage current density compared with CeB₆ FETs, and this further demonstrates the feasibility of the introduction of Al₂O₃ to reduce the leakage current density; the maximum drain-source current density is −114.6, −96.0, −80.9, and −73.7 mA/mm, which may be benefited from the well-protected channel. For the 12 μm L_G devices, the saturation carrier mobility is 593.6 cm²/V s, demonstrating a good channel transport characteristic. This work may provide a promising strategy for the application of normally off H-diamond FETs significantly.