Suppressing the Leakage of GaN HEMTs on Single-Crystalline AlN Templates by Buffer Optimization

Single-crystalline AlN templates are a promising substrate choice for GaN power HEMTs, which have, however, seldom been investigated. In this work, high-performance GaN HEMTs on 2-in AlN templates are successfully demonstrated and evaluated. The buffer lateral leakage was significantly suppressed by five orders of magnitude by epitaxially growing an AlN nucleation layer to deactivate the impurities of Si and O, which are introduced at the interface of buffer/AlN template during the secondary epitaxy. An exceptionally high lateral blocking voltage exceeding 10 kV was attained with a spacing of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$100~\mu $ </tex-math></inline-formula> m. HEMTs without any field plate structure showcase an outstanding breakdown voltage of over 8 kV and an on/off ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{{9}}$ </tex-math></inline-formula>. The dynamic <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{\text{on}}$ </tex-math></inline-formula> degradation is limited to be within 20%, and the threshold voltage <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {th}}$ </tex-math></inline-formula> exhibits a 10% shift after off-state stress. High-performance GaN HEMTs demonstrated in this work prove that the single-crystalline AlN templates are promising for future high-reliability power HEMTs.