A Compact Surface Potential Model for Flexible Radio Frequency AlGaN/GaN High-Electron-Mobility Transistor

Abstract

Compact model of flexible radio frequency (RF) electronic devices is crucial for flexible circuit designs. In this article, a compact model, including external strain effects for flexible RF gallium nitride (GaN) high-electron-mobility transistor, is presented. First, the carrier density and threshold voltage with external mechanical uniaxial strain is analytically characterized by introducing the strained piezoelectric charge <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta \sigma $ </tex-math></inline-formula> , Schottky barrier height <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta \phi _{B}$ </tex-math></inline-formula> , and surface state density <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D_{\mathrm {it}}$ </tex-math></inline-formula> into the model. Then, the variations of the conduction band offset at the AlGaN/AlN and AlN/GaN interfaces are considered. Finally, the complete large-signal model is established after embedding strain effect into intrinsic drain current and nonlinear capacitance models. The proposed model is verified by measurements, including direct current <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V$ </tex-math></inline-formula> characteristics, small-signal <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> -parameters up to 40 GHz, and large-signal power performance—output power, efficiency, and gain. The proposed model will be useful for the RF application of flexible electronics.