Hydrogen “doped” thin film diamond field effect transistors for high power applications

Abstract

Early predictions that diamond would be a suitable material for high performance, high power devices were not supported by the characteristics of diodes and field effect transistors (FETs) fabricated on boron doped ( p-type) thin film material. In this paper commercially accessible polycrystalline thin 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 5×10 17 cm −3. Schottky diodes and metal–semiconductor FETs (MESFETs) have been fabricated using this approach which display unprecedented performance levels; diodes with a rectification ratio >10 6, leakage currents <1 nA, no indication of reverse bias 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 been fabricated. Predictions based upon experiments performed on these devices 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 all be an interesting material for power applications.