Normally-off hydrogen-terminated diamond field effect transistor with a bilayer dielectric of Er₂O₃/Al₂O₃

A normally-off hydrogen-terminated diamond field effect transistor with an Er₂O₃/Al₂O₃ bilayer dielectric was fabricated. Dielectric materials Er₂O₃ and Al₂O₃ were deposited on H-diamond surface using radio frequency sputtering and atomic layer deposition, respectively. The threshold voltage of the device was −0.49 V at V_DS of −20 V, which indicated a normally off characteristic, that could be attributed to the low work function of Er₂O₃ and the polar character of amorphous Er₂O₃. The maximum drain-source current for the hydrogen-terminated diamond field effect transistor with 6 μm gate length was −16.1 mA/mm and the sheet carrier density integrated was 1.08 × 10¹³ cm⁻². The maximum effective hole mobility was 110.47 cm²/V·s and the interfacial trapped charge density was 3.16 × 10¹² eV⁻¹ cm⁻². This bilayer dielectric of Er₂O₃/Al₂O₃ provides an alternative plan for the fabrication of normally-off diamond device.