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

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 Delta sigma , Schottky barrier height $Delta phi_{B}$ , and surface state density $D_{{it}}$ 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 I-V characteristics, small-signal S-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.