Microwave Power Characteristics Of AlGaN/GaN HEMT

With the rapid development, a microwave system requires higher performance of solid-state power devices. A traditional GaAs device cannot meet the requirement. As the next generation of solid-state device, AlGaN/GaN High Electronic Mobility Transistor (HEMT) has higher output power, higher work frequency, and can endure higher channel temperature and radiation. Therefore, AlGaN/GaN HEMT becomes promising candidate of high frequency, high output power microwave power devices which are needed in mobile communication and radar system, etc.This paper is focused on the research of microwave power character of AlGaN/GaN HEMT.The small-signal equivalent circuit model of GaAs devices has been revised and used to extract the parameters of AlGaN/GaN HEMT since the principles both of them are almost the same. The gate length and the gate width of the used deviceis were 0.4μm and 1mm, respectively. The output equivalent impendence through the Load-Pull test was also obtained.With these parameters, the AlGaN/GaN internally matching transistor was designed and muanufactured. The transistor delivered an output power of more than 5W with a power gain of more than 6dB and the typical power-added efficiency of 30% at frequency from 7.5 to 9.5 GHz. This performance is better than GaAs device. The test results were consistent with the results of predict, which showed that the model parameters were suitable for engineering application.Although AlGaN/GaN HEMT can endure higher channel temperature in theory, it generates more dissipation power. Therefore, the thermal design is very important. The thermal model has been established in this paper. Simulation and analysis of distributing of channel temperature of GaAs microwave power device were carried out by using the thermal balance equations and Ansys software. The results were equal to those of the measurement. That is, this method can be used in thermal design of GaAs device. The possibility of this method to be used to optimize thermal design of AlGaN/GaN HEMT was also discussed.