RF power performance of submicron MESFET on hydrogen terminated polycrystalline diamond

Diamond is in principle the highest performance widegap semiconductor; its outstanding electronic and thermal properties make it an attractive material for high power radiofrequency (RF) and microwave electron devices. Even though the properties of synthetic diamond have been known from many years, only recently significant technology advances in the growth of single-crystal and polycrystalline diamond have fostered the research on high-performance diamond electronics. In this framework, the use of polycrystalline diamond as a substrate offers the advantage of larger areas and lower cost with respect to single-crystal diamond. Available approaches for the control of diamond conductivity rely mainly (up to now) on p-type doping, either through extrinsic doping with boron, or exploiting hydrogen (H) surface termination, which induces a quasi-2D hole channel a few nanometers below the surface. Both approaches have been pursued to develop high speed power FETs [1], with record cut-off frequency (45 GHz) achieved by H-terminated FETs on polycrystalline diamond [2]. Despite such promising small-signal performances, only a few examples of RF power measurements have been reported so far, limited at comparatively low frequency (1 GHz), and only for single-crystal diamond FETs, with record performance of 2W/mm [3]. In this paper, we present RF power measurements of submicron H-terminated FETs on polycrystalline diamond up to 2 GHz, showing the potential of such substrate for the development of microwave power devices.