High performance ionic-liquid-gated air doped diamond field-effect transistors.

We report successful fabrication of high performance ion-gated field-effect transistors (FETs) on hydrogenated diamond surface. Investigations on the hydrogen (H)-terminated diamond by Hall effect measurements shows Hall mobility as high as ~200 cm2/Vs. In addition we demonstrate a rapid fabrication scheme for achieving stable high performance devices useful for determining optimal growth and fabrication conditions. We achieved H-termination using hydrogen plasma treatment with a sheet resistivity as low as ~1.3 k/sq. Conductivity through the FET channel is studied as a function of bias voltage on the liquid ion-gated electrode from -3.0 to 1.5 V. Stability of the H-terminated diamond surface was studied by varying the substrate temperature up to 350oC. It was demonstrated that the sheet resistance and carrier densities remain stable over 3 weeks in ambient air atmosphere even at substrate temperatures up to 350oC, whereas increasing temperature beyond this limit has effected hydrogenation. This study opens new avenues for carrying out fundamental research on diamond FET devices with ease of fabrication and high throughput.