GaN Super-Heterojunction FETs With 10-kV Blocking and 3-kV Dynamic Switching
Jesse T. Kemmerling, Rian Guan, Mansura Sadek, Yixin Xiong, Jianan Song, Sangwoo Han, Sundar Babu Isukapati, Woongje Sung, Rongming Chu
Abstract
This article reports on two generations of GaN-on-sapphire super-heterojunction (SHJ) transistors, aiming at the realization of 10-kV class power transistors with low static and dynamic ON-resistance. First generation (Gen. 1) GaN SHJ-FETs used a single 2-D electron gas (2DEG) channel design with Schottky gate. Experimental results indicated the feasibility of achieving 10-kV blocking, however, room for improvement to reduce static source-to-drain ON-resistance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {DS},\text {ON}}$ </tex-math></inline-formula> and dynamic <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {DS},\text {ON}}$ </tex-math></inline-formula> degradation. A second generation (Gen. 2) SHJ-MOSFET was designed using an epitaxy with two 2DEG channels for larger ON-state drain current and smaller <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {DS},\text {ON}}$ </tex-math></inline-formula> . The high-voltage capability and dynamic <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {DS},\text {ON}}$ </tex-math></inline-formula> degradation mitigation were reached by implementing the GaN SHJ design, while simultaneously avoiding surface trapping between the gate and the SHJ structure. Gen. 2 experimentally showed scaling of blocking voltage with SHJ length up to 10 kV, reduced static <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {DS},\text {ON}}$ </tex-math></inline-formula> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$71.4~\Omega \cdot $ </tex-math></inline-formula> mm (73.5 <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> cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{{2}}{)}$ </tex-math></inline-formula> , low <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {DS,ON}}{C}_{\mathrm {O(}\mathrm {tr})}$ </tex-math></inline-formula> of ~4.9 ps, and controlled current collapse of 123% when switched from an OFF-state bias of 3 kV.