Reliable Parameter Extraction of Asymmetric GaN-Based Heterojunction Field Effect Transistors

A novel reliable small signal model parameter extraction of asymmetric GaN-based Heterojunction Field Effect Transistors (HFETs) is proposed in this paper. An efficient systematic searching procedure based on pinch-off and cold weak-forward S-parameters has been developed to consider the asymmetric structure of GaN HFETs and find the optimal values of the gate and drain pad capacitances $C_{pg}$ and $C_{pd}$. Considering that the depletion region extension is varied with the gate bias voltage Vgs slightly even below pinch-off voltage, the obtained initial values of the extracted parameters are optimized by artificial bee colony (ABC) algorithm to improve the reliability of parameter extraction. The developed parameter extraction method shows excellent accuracy and reliability. The proposed procedure can be extended to asymmetric GaN devices with various process technologies. The developed approach has been validated by an asymmetric $0.15 \mu \mathrm{m}$ GaN HFET over a wide range of bias conditions and frequencies.