Characterization of sub-micron in-plane devices in H-terminated diamond

The highly conductive p-type surface layer that can be induced in diamond by hydrogen termination is very attractive for electrical applications and in particular for the design of in-plane devices. In this paper we will present our work on the characterization of sub-micron in-plane transistors. Two different approaches have been analyzed for the design of the transistor gate. First of all the properties of Al gates on H-terminated diamond will be discussed, focusing on their capacitance-voltage characteristics. As a result of this study it will be shown how the p-type surface layers in H-terminated diamond behaves like a two-dimensional system. However, due to the poor channel control by the Al gates another approach was followed. The gate region is separated from the channel by a thin oxidized line. The channel current is controlled by the voltage applied to the gate, which varies the space charge region width that is formed at the oxidized line. Sub-micron gate structures were generated by using e-beam lithography and a plasma oxidation treatment. The transistor characteristics of the in-plane diamond structures are presented in this paper.