Tuning of Quasi-Vertical GaN FinFETs Fabricated on SiC Substrates
Philipp Gribisch, Rosalía Delgado Carrascón, Vanya Darakchieva, Erik Lind
Abstract
In this work, we present the fabrication and investigation of the properties of quasi-vertical gallium nitride (GaN) fin field effect transistors (FinFETs) on silicon carbide (SiC) substrates and the influence of a postgate metallization annealing (PMA). The devices reveal low subthreshold swings (SSs) down to around 70 mV/dec. For a 1- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> -thick drift layer, a low ON-resistance below 0.05 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{m}\Omega \cdot $ </tex-math></inline-formula> cm2 (normalized on the fin area) and a breakdown voltage of 60 V were obtained. Devices with included PMA show a decreased threshold voltage and ON-resistance and by several orders of magnitude reduced gate leakage current compared to non-annealed devices. The devices show ohmic contact behavior and slightly negative threshold voltages, which indicates normally- ON behavior. The effective and field-effect mobility of the fin channel was obtained with a modeled carrier concentration and reveal to around 70 and 13 cm2/(Vs) at high gate voltages, which is in a good comparison to so far reported similar devices.