A Study On The Modeling Of AlGaN/GaN High Electron Mobility Transistors

Gallium Nitride (GaN) is the most important one of the third generation semiconductors and a promising materials in power microwave, high temperature, optoelectronics, and radiation resistant applications due to its excellent physical properties and chemical stabilities, such as wide band gap, high electron saturated velocity, high breakdown electric field, high power density, etc. Now, studies on GaN based materials have been a focus of intensive attention at domestic and international.AlGaN/GaN high electron mobility transistor (HEMT) is a kind of GaN device based on the AlGaN/GaN heterojunction. Comparing with the traditional MESFET transistors, AlGaN/GaN HEMTs own the outstanding performances of high transconductance, high output current density and high cutoff frequency, showing great potentiality in the applications of high temperature, high frequency and great power.The researches of AlGaN/GaN HEMTs have been performed for many years. However the reliable AlGaN/GaN HEMTs have not been utilized commercially now. Besides the problems of reliability and defects in the GaN materials, the high power dissipation of AlGaN/GaN HEMTs operating at large biases may result in high junction temperature and enhance phonon scattering causing a drop of carrier mobility. This effect has been reported to be of great influence on the static current characteristics, and is commonly referred to as"self-heating". The self-heating effect may degrade the gate electrode due to accelerated electromigration, and can easily burn metal wires connecting the chip to the package, thus causing device failures and reliability problems. Severe self-heating may even damage the device itself. On the other hand though AlGaN/GaN HEMTs have a bright future in the applications of high frequency, the small signal and large signal models for them are scarce. Most of the models are based on MESFETs, which ignore the peculiarity of HEMTs. Therefore the discrepancy between the theoretical result and experimental data exists. So it is necessary to develop an analytical model for AlGaN/GaN HEMTs, which is clear in device mechanism description and simple in calculation to be suitable for the design and optimization of device.