Investigation of electron divices for hard atmosphere using heteroepitaxial diamond layr

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1) Development of large area microwave plasma CVD using coaxial waveguide :Using coaxial waveguide new type of microwave plasma CVD has been developed. The following results have been obtained. a) Enlargement of plasma, b) controllability of ion energy (20-30 eV) necessary for diamond nucleation, and c) stability of plasma above 200 Torr where the improvement of crystallinity has been expected.2) Observation of initial growth stage of heteroepitaxial diamond :Using high resolution SEM the surface structure of SiC necessary for diamond nucleation has been investigated. Based on the observation the high density of nucleation leading to smooth heteroepitaxial growth has been realized as a result.3) MESFET fabrication on the heteroepitaxial diamond layrs :Metal semiconductor field effect transistors (MESFETs) with 5mum gate length have been fabricated on the heteroepitaxial diamond layrs. The performance of the devices are comparable to those on homoepitaxial diamond surfaces. The obtained transconductance (gm) are 7-8mS/mm, which is the highest in diamond heteroepitaxial layr. It reflect the high hole mobility of the heteroepitaxial layr.4) NAND,NOR,R-S flip-flop circuits and MOSFET :On homoepitaxial layr, NAND,NOR,and R-S flip-flop circuits have been operated. The MOSFETs with the gm of 15mS/mm comparable to Si n-MOSFET have been developed and operated up to 350ﾟC.This result is the most advanced one in diamond FETs