Report of GaN HEMTs on 8-in Sapphire
Junbo Wang, Xiangdong Li, Long Chen, Tong Liu, Zhanfei Han, Shuzhen You, Lezhi Wang, Zilan Li, Yue Hao, Jincheng Zhang
Abstract
The two crucial factors of large scale and high voltage can hardly be balanced for the traditional GaN HEMTs on Si substrates. Recently, one promising solution, GaN-on-sapphire, has attracted great attention. However, the commercialized GaN-on-sapphire wafers ever reported are usually 6 in. It is urgent to develop 8-in GaN-on-sapphire to reduce the cost and meet the market demands. In this work, to the best of our knowledge, an 8-in GaN-on-sapphire wafer is demonstrated for the first time. The sheet resistance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{R}_{{\Box}} $</tex-math> </inline-formula> exhibits a wafer-level nonuniformity of 4% and an average value of 310 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\bm\Omega/\Box$</tex-math> </inline-formula> , and the warpage is kept to 30 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $</tex-math> </inline-formula> m, by dedicatedly tuning the 1.98- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $</tex-math> </inline-formula> m buffer stack. The fabricated 200-V HEMTs exhibit a low <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{R}_{\biosc{on}}$</tex-math> </inline-formula> of 6.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\bm\Omega \cdot\text{mm}$</tex-math> </inline-formula> , a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{V}_{\text{TH}}$</tex-math> </inline-formula> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 4.2 V, and an OFF-state breakdown voltage above 500 V without any field plate. The electrical mapping visualizes <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{R}_{\biosc{on}}$</tex-math> </inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{V}_{\text{TH}}$</tex-math> </inline-formula> distributed in concentric circles across the wafer. Generally, this work demonstrates the feasibility of realizing 8-in GaN-on-sapphire for power electronics applications in the future.