Gate-Bias Induced Threshold Voltage (<i>V</i> <sub>TH</sub>) Instability in P-N Junction/AlGaN/GaN HEMT
Zuoheng Jiang, Lingling Li, Chengcai Wang, Junlei Zhao, Mengyuan Hua
Abstract
In this work, we studied 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">${V}_{TH}$ </tex-math></inline-formula> ) instability in E-mode p-n junction (PNJ)/AlGaN/GaN high-electron-mobility transistor (HEMT) using pulsed- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}/{V}$ </tex-math></inline-formula> measurement and positive bias temperature instability (PBTI) test. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{TH}$ </tex-math></inline-formula> shifts positively under forward gate bias, which is ascribed to electron trapping in the gate-stack region. Benefiting from the special p-GaN/n-GaN junction, reduced electric field suppresses electron trapping in the PNJ gate, resulting in more stable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{TH}$ </tex-math></inline-formula> compared with the conventional Schottky-type p-GaN gate. Specifically, less positive threshold voltage shift ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{TH}$ </tex-math></inline-formula> ) is observed under higher temperatures, or after being stressed for a prolonged period with gate bias exceeding 6 V. The decrease in positive <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{TH}$ </tex-math></inline-formula> results from enhanced hole injection and especially hole trapping in the p-GaN/n-GaN interdiffusion region, which compensates for electron trapping and reduces positive <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{TH}$ </tex-math></inline-formula> .