Si-diffused GaN for enhancernent-mode GaN MOSFET on Si applications

Si diffusion into GaN was studied as a function of encapsulant type (SiO2 or SiNx) and diffusion temperature. Using a SiO2 encapsulant, the Si diffusion exhibited an activation energy of 0.57 eV with a prefactor of 2.07 X 10(-4) cm(2) sec(-1) in the temperature range 800-1,000 degrees C. An enhancement-mode MgO/GaN-on-Si metal-oxide semiconductor field-effect transistor (MOSFET) was fabricated utilizing Si-diffused regions under the source and drain to provide an accumulated channel. The gate leakage through the undoped GaN was low enough for us to achieve good saturation behavior in the drain-current-voltage characteristics. The devices showed improved transconductance and drain current relative to previous devices with Si-implanted source/drain regions.