First Demonstration of Optically-Controlled Vertical GaN finFET for Power Applications
Jung-Han Hsia, Joshua Perozek, Tomás Palacios
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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {{30}}~\mathbf { \textit {mW}/\textit {cm}^{{2}}}$ </tex-math></inline-formula> . The proposed devices were then experimentally demonstrated with an on-current density greater than 90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {A/\textit {cm}^{{2}}}$ </tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {V_{\textit {DS}}}$ </tex-math></inline-formula> = 3 V, triggered by a few <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> Ws of UV LED power. Despite having relatively high dark currents, the devices have shown maximum optical responsivity greater than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {{10}^{{5}}}~\mathbf {A/{W}}$ </tex-math></inline-formula> 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.