Diamond FET Technology for Power Electronics

Amongst the traditional wide band-gap materials diamond has suffered in terms of the relative immaturity of both substrate and processing technology. However, recent developments in both these aspects have now made the development of diamond devices for power devices a realistic prospect; within the framework of the European GreenDiamond collaboration (2015-2020), all aspects required for the realisation of the first HVDC diamond based converter were considered. These included diamond device design, substrate qualification/preparation, diamond epitaxy, device processing technology, packaging and power converter design. At the heart of field effect transistor technology lies the MOS channel; breakthrough technology in the formation of γ-Alumina gate oxide with controlled band offset allowing an effective barrier to hole leakage from the channel has been demonstrated [1]. Device design specifically suited to diamond’s wide band-gap properties is also essential, an example being the ‘deep-depletion’ diamond MOSFET concept also recently demonstrated [2]. In terms of diamond MESFET technology, the use of ‘Reverse-blocking’ devices where the drain on the diamond device structure is Schottky, as opposed to the conventional ohmic contact, has proved highly effective [3]. Diamond FET structures that rely upon low damage etching procedures have also been developed [4]. This paper will use what has been learnt from the GreenDiamond programme to highlight the current status of diamond FET technology and discuss the challenges that must still be met.<br/>[1] Canas <i>et al.,</i> Appl. Surf. Sci., <u>535</u> (2021) 146301<br/>[2] Masante <i>et al.,</i> J. Phys. D: Appl. Phys. <u>54</u> (2021) 233002<br/>[3] Canas <i>et al.,</i> IEEE Trans Elec. Dev., (2021) DOI 10.1109/TED.2021.3117237<br/>[4] Hicks <i>et al.,</i> Sci. Rep., <u>9</u> (2019)15619<br/>This work was supported by the European Commission “GREENDIAMOND” through the H2020 Large Project under Grant SEP-210184415.