Normally-off HEMTs With Regrown p-GaN Gate and Low-Pressure Chemical Vapor Deposition SiN_x Passivation by Using an AlN Pre-Layer

Abstract

Normally-off HEMTs have been fabricated with regrown p-GaN gate and SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> passivation by Low-pressure chemical vapor deposition (LPCVD) using an AlN pre-layer, featuring a high-temperature passivation-first technique with no incompatibility issues. Through careful surface treatments, high-quality interfaces (regrown p-GaN/AlGaN and SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> / AlGaN), as well as a stable p-GaN contact, can be achieved, enabling a robust gate operation and improved dynamic performance. The as-fabricated device exhibits a low reverse gate leakage of 2 nA/mm @ V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GD</sub> = -200 V, a stable forward gate current of 10 μA/mm @ V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</sub> = 5 V, a positive threshold voltage of +1.7 V @ I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> = 10 μA/mm with a high saturation current of 435 mA/mm, a high I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</sub> /I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</sub> ratio of 5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> , and a low R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on,d</sub> /R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on,s</sub> ratio of 1.5. The as-developed technique with the LPCVD SiN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> passivation and p-GaN gate regrowth may provide a way to enhance the performance of p-GaN E-HEMTs.