Novel in-plane gate devices on hydrogenated diamond surfaces

Hydrogen-terminated diamond surfaces are very attractive for devices based on surface electronics. The hole channel that governs the surface conductivity and the simplicity of the surface patterning are key features which allow a large flexibility for device design. In-plane gate field effect transistors have been fabricated with the conductive channel separated from the ohmic gate contacts by insulating thin lines, obtained by using a combination of electron beam lithography with surface oxidation. Depletion regions spreading from the highly resistive oxidized lines which separate the channel and gate regions can be controlled by applying a voltage to both lateral gate contacts. A wire structure has been designed in such a way that the gate voltage effectively modulates the conductance of the channel. The channel modulation is discussed in terms of a quasi two-dimensional surface carrier density. The effect of surface defects on the transistor properties has also been investigated.