|dc.description.abstract||In this thesis,the device characteristics and device modeling technologies of enhancement-mode pHEMTs are investigated. Firstly, the device physics and non-linear characteristics of enhancement-mode pHEMTs are studied, including gain compression and harmoic distortion. By cold-FET measurement and Yang-Long dc measurement, the extrinsic elements of small-signal model can be estimated accurately. The other intrinsic parameters of small-signal can be determined based on the matrix transformation with the on wafer measured S-parameters.The intrinsic model elements, such as Cgs, Cgd, Cds, Rds, Gm,τ and Ri can be extracted under different Vds and Vgs bias points.
In this study we propose a modified large-signal model for enhancement-mode pHEMTs, which is based on the conventional Curtice model. The modified large-signal model is based on the structure of Curtice model. In order to take the device non-linear behaviors into consideration, instead of using traditional junction capacitances (Cgs, Cgd), channel resistance (Ri), and output resistance (Rds), we propose suitable non-linear equations to describe these elements, which are the functions of Vgs and Vds. We also examine the accuracy of the large-signal model. Using scalable parasitic components attached to the modified large-signal model, a completed RF large-signal model covering various gate-widths can correctly predict the device’s dc and rf characteristics. Using thise model, a 2.4 GHz microwave amplifier was designed and tested.||en_US|