First Demonstration of Optically-Controlled Vertical GaN finFET for Power Applications

Abstract

In this work, we propose a novel optically-controlled vertical GaN finFET directly triggered by low-power ultraviolet (UV) illumination. The proposed device consists of a normally-off, vertical GaN finFET with an optically transparent illumination window. Electron-hole pairs are generated in the depleted fin channel upon 365 nm illumination to turn on the device. The operating principle of optically-controlled, vertical finFETs was first confirmed through simulations where 5 orders of magnitude on-off current ratio were predicted under an illumination intensity of 30~ it mW/it cm^2. The proposed devices were then experimentally demonstrated with an on-current density greater than 90 A/it cm^2 at V_it DS = 3 V, triggered by a few μ Ws of UV LED power. Despite having relatively high dark currents, the devices have shown maximum optical responsivity greater than 10^5~ A/W owing to the strong photovoltaic effects in the highly scaled fins. These initial results demonstrate the potential of our proposed device to enable future high-power systems with greatly enhanced electromagnetic interference (EMI) immunity, simplicity, cost-effectiveness, and reliability.