Thin-Barrier E-Mode GaN-Based MIS-HEMT with High Saturation Current Using AlSiO Composite Gate Dielectric

For enhancement-mode (E-mode, also known as normally-off) GaN-based metal-insulator-semiconductor high electron mobility transistors (MIS-HEMTs), which are characterized by improved safety and reliability, the design of the gate dielectric layer is deemed crucial. A composite dielectric material, AlSiO, has been fabricated in this work using atomic layer deposition (ALD), combining the negative fixed charge properties of aluminum oxide <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\text{Al}_{2}\mathrm{O}_{3})$</tex> and the high breakdown field of silicon oxide <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\text{SiO}_{2})$</tex>. Then the composite material is employed as the gate dielectric for thin-barrier recessed-gate GaN-based HEMTs. Normally-off operation with threshold voltage <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathrm{V}_{\text{th}})$</tex> of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1\sim 1.5\mathrm{V}$</tex> is achieved while the breakdown field is improved to 9 MV/cm in devices using the AlSiO composite dielectric. The maximum saturation current reaches 1500 mA/mm and further increases to 1900 mA/mm after annealing. The predicted lifetime is expected to exceed 10 years at an operating voltage of 5.58 V. These research findings suggest that the AlSiO composite dielectric is an effective solution to balance the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{V}_{\text{th}}$</tex> and breakdown field in E-mode GaN-based MIS-HEMTs, providing new insights and directions for future gate dielectric design.