Research Of High Power GaN HEMT Device Modeling

As CMOS process steps into lOnm era, whether Moore Law still works remains controversial.While scientists keep exploring new materials, GaN stands out thanks to its wide bandgap, high breakdown voltage and high electron mobility properties. It can be used in many applications such as radar,satellite and mobile base stations. Despite excellent performances of GaN devices, design efficiency may be reduced because of the complex electrical characteristics, failing to develop the devices’ full performance potentials. A large signal model which can predict the perfomance of GaN HEMT devices is very important. This thesis will focus on the key point of GaN device modeling:Ⅰ-Ⅴ equation and trapping effect. Some theoretical analysis and compared measurement result will be presented.The key issue of device modeling is output drain current variation versus the gate voltage and drain voltage. This thesis will analyze the Ⅰ-Ⅴ model selection and creation process. We find that the Angelov can not fit the measurement data accurately, through the relationship of model parameters change with external bias voltage. This paper will proposed a new Ⅰ-Ⅴ equation based on Angelov model, through modify the paremeter φ、α、Vpkm. Then some compared measurement result will be presented to show its accurate enough.It’s very important to do the trapping effect modeling, in order to describe the output current of GaN device correctly. There has already some research on trapping effect model. But these models often describe part of electrical properties induced by trapping effect. And also these models can not give a good discrition when the device is excited by RF signal. This paper introduces the mechanisms of traps and also its relationship between capture、emission process and external bias voltage. And also the various electrical properties induced by trapping effect will be presented. This thesis addresses the trapping effect through devided it into two part:gate-lag and drain-lag effect. We propose a bais-dependent method to deal with gate-lag effect, and use drain-lag subcircuit to deal with drain-lag effect. The drain-lag subcircuit can discribe the whole behavior of capture and emission process. This method make the model more close to the realistics working condition. The measurement and simulation result of trapping effect model will be presented.