.algan / Gan Hemts Device Modeling And Power Synthesis Of Research

Gallium Nitride (GaN) is the most important one of the third generation semiconductors and AlGaN/GaN high electron mobility transistors (HEMTs) are excellent for high frequency, high power, high temperature, anti-radiation electronics. Accurate device modeling is very important for RF and microwave circuit, which can improve the accuracy of circuit designs and shorten the design time, This thesis has mainly established a AlGaN/GaN HEMT equivalent circuit model, and based on the model presented, a GaN HEMT microwave power combination circuit is designed with the software ADS.First, a small signal equivalent circuit topology for GaN HEMT and a method for broadband determination of the small-signal model are proposed. The established small-signal equivalent circuit model is quite simple, accurate and broadband (0-10GHz), and is very useful for large signal characteristics analysis.Then, account for obvious self-heating effect of GaN HEMTs, a large signal equivalent circuit model improved by the Curtice cubic nonlinear model is proposed, where the equation for drain current is determined self-consistently by use of the channel temperature computed from a thermal circuit. The improved large signal model shows good agreement with measured I-V curves. Next, large signal models for capacitances of AlGaN/GaN HEMT are discussed in detail.Finally, to obtain the high output power, a GaN HEMT microwave power combination circuit based on the established model is designed with the software ADS (Advanced Design System), using microstrip Wilkinson power splitter/synthesizers. With 25V supply voltage, calculated output power and power added efficiency are 3.5W and 32% at 3.5GHz.