An optically activated diamond field effect transistor

Thin film diamond photodetectors are one of the most promising classes of d iamond devices for commercial exploitation. Already, photoconductive device s which display extremely high levels of selectivity between deep UV and vi sible light, allied to good sensitivity, are becoming available. However, m ore advanced device designs are required if high speed operation is to be a chieved alongside high sensitivity. Phototransistors are ideally suited to this application, but until recently room temperature operation of diamond field effect transistors (FETs) was not possible. This has changed with the emergence of p-type hydrogenated diamond and this paper describes the fabr ication and operation of the first MESFET based diamond photodetectors (OPF ETs) to be made. Optical modulation has been demonstrated and the wavelengt h selectivity measured. Devices respond significantly more to UV light than visible wavelengths, with gain levels of around 4. The mechanism(s) of ope ration are discussed. (C) 1999 Elsevier Science S.A. All rights reserved.