Report of GaN HEMTs on 8-in Sapphire

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 $\textit{R}_{{\Box}} $ exhibits a wafer-level nonuniformity of 4% and an average value of 310 $\bm\Omega/\Box$ , and the warpage is kept to 30 $\mu $ m, by dedicatedly tuning the 1.98- $\mu $ m buffer stack. The fabricated 200-V HEMTs exhibit a low $\textit{R}_{\biosc{on}}$ of 6.5 $\bm\Omega \cdot\text{mm}$ , a $\textit{V}_{\text{TH}}$ of $-$ 4.2 V, and an OFF-state breakdown voltage above 500 V without any field plate. The electrical mapping visualizes $\textit{R}_{\biosc{on}}$ and $\textit{V}_{\text{TH}}$ 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.