| 摘要: | 隨著微波技術的日趨重要，對主動元件的要求也愈來愈高，而傳統砷化鎵金屬-半導體電晶體(MESFET)在功率上的表現已不敷使用。異質結構高速場效電晶體(HEMT)、異質接面雙載子電晶體(HBT)在高頻電路的角色愈來愈顯重要。本論文是以增強型異質結構高速移導率電晶體(enhancement-mode HEMT)元件特性探討與模型化技術為主。 本論文首先討論異質結構高速場效電晶體的工作原理，探討元件的非線性特性，包括功率增益壓縮、諧波失真等。並利用Cold FET等量測方法萃取元件內外部等效電路參數以建立小訊號模型，對內部本質元件的非線性特性加以分析。之後，結合電壓-電流方程式以及非線性電阻、電容方程式，建立元件之大信號模型，並與量測之直流、高頻功率特性及線性度作比較。最後，我們將大信號模型實際用於電路設計，設計一2.4GHz微波放大器。 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. |
