High-Performance Enhancement-Mode Al<sub>2</sub>O<sub>3</sub>/AlGaN/GaN-on-Si MISFETs With 626 MW/<inline-formula> <tex-math notation="LaTeX">$\mathrm{cm}^{2}$ </tex-math></inline-formula> Figure of Merit

Abstract

In this paper, the partial gate recess for performance improvement of enhancement-mode (E-mode) GaN power devices is experimentally demonstrated. The gate recess with a careful control of the recess depth was performed with an optimized recessed barrier thickness of ~1.5 nm that is thin enough to completely deplete the 2-D electron gas channel in the gate region. Meanwhile, the remaining barrier preserves the as-grown quantum well of the heterostructure physically intact and thus, effectively mitigates the lattice damage caused by gate recess. The fabricated E-mode Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /AlGaN/GaN MISFETs deliver a threshold voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub> ) of +1.5 V. The maximum drain current density (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D,max</sub> ) and transconductance (G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m,max</sub> ) are 693 mA/mm and 166 mS/mm, respectively. The MISFETs with an L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GD</sub> of 10 μm feature an OFF-state breakdown voltage of 860 V at a leakage current of 1 μA/mm. The corresponding specific ON-resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON,sp</sub> ) is as low as 1.18 mΩ·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> yielding a high-power figure of merit of 626 MW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . In comparison with the reference MOSFETs by fully gate recess, the respectably improved device performance of the MISFETs attributes to the enhanced electron mobility achieved by the partial gate recess.