Optically-Gated InP-MISFET: A New High-Gain Optical Detector

Abstract

A new optical detector with an enhancement-mode MISFET structure is demonstrated. This device consists of a semi-transparent gate metal and a pyrolitic Al₂O₃ insulator film formed on an Fe-doped semi-insulating InP-crystal. A photocurrent-gain higher than 10³ has been obtained under application of a gate bias. Moreover, a gate voltage lower than 2 V is high enough to give this large amplification. The amplification mechanism is explained by an increase in the surface-channel conductivity via the development of an electron quasi-Fermi level shift toward the conduction-band edge under the illumination.