Hydrogen "doped" thin film diamond field effect transistors for high powerapplications

Early predictions that diamond would be a suitable material for high perfor mance, high power devices were not supported by the characteristics of diod es and field effect transistors (FETs) fabricated on boron doped (p-type) t hin film material. In this paper commercially accessible polycrystalline th in film diamond has been turned p-type by the incorporation of near surface hydrogen; mobility values as high as 70 cm(2) V-1 s(-1) have been measured for films with a carrier concentration of 5 x 10(17) cm(-3). Schottky diod es and metal-semiconductor FETs (MESFETs) have been fabricated using this a pproach which display unprecedented performance levels; diodes with a recti fication ratio > 10(6), leakage currents < 1 nA, no indication of reverse b ias breakdown at 100 V and an ideality factor of 1.1 have been made. Simple MESFET structures that are capable of switching V-DS values of 100 V with low leakage and current saturation (pinch-off) characteristics have also be en fabricated. Predictions based upon experiments performed on these device s suggest that optimised device structures will be capable of operation at power levels up to 20 W mm(-1), implying that thin film diamond may after a ll be an interesting material for power applications. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.