Simulation Research On Microwave Power Characteristics Of AlGaN/GaN HEMT Devices

AlGaN/GaN HEMT device has the advantages of high operating voltage,high electron saturation speed and high two-dimensional electron gas concentration,which can meet the requirements of power amplifier(PA)for high operating frequency and high power density.It is suitable for preparing gallium nitride microwave power devices and is the preferred single-tube device for PA research.It is often used in radar,communication system acer station and other important military fields.As one of the most basic units in wireless communication system,high power density and high efficiency are the main performance indexes of power amplifier.Currently,AlGaN/GaN HEMT devices are mainly used in high frequency applications,achieving high signal power densities of 20.9 W/mm@10GHz in xband and record fT and Fmax at 128 GHz and 255 GHz.However,due to the low output power density of gallium nitride devices at high frequency(such as microwave and W band),the device is difficult to achieve the optimal output power density.In this context,a series of variation rules of dynamic load lines and microwave power characteristics are explored by adjusting device structure and operating frequency parameters,and the factors limiting the output power of hf AlGaN/GaN HEMT devices are further studied.The main research work and achievements are as follows:(1)The AlGaN/GaN HEMT device model was established based on Silvaco TCAD software.The square resistance of 0.55 K ω/Sq obtained by simulation was similar to that of 0.6 K ω/sq measured by experiment,which verified the accuracy of the device model.The maximum electric field intensity of the device is 3 MV/cm.The field plate structure is used to modulate the electric field peak at the electrode edge channel,so that the electric field peak at the electrode edge of the device is consistent with that at the field plate edge.The results show that the maximum drain operating voltage of the source field plate structure is much larger than that of the gate field plate.(2)The large signal microwave power characteristics of AlGaN/GaN HEMT devices are studied by adjusting the external impedance and drain operating voltage.The external impedance parameter Cd increases,the large signal dynamic load line widens,Rd increases,and the dynamic load line of the device moves towards the knee voltage.The Rd of the device increases by 200 ω on average for every 25 V increase in drain operating voltage.The results show that increasing the load impedance can further improve the power characteristics of the device.(3)The microwave power characteristics of AlGaN/GaN HEMT devices are studied by adjusting the operating state and frequency of the devices.The Pout of the relatively small input power(20 dBm)in the Class A amplifier is the maximum,4.0 W/mm,and the PAE of the device in the Class B amplifier is the maximum,30%@10 GHz.The results show that the grid displacement current increases with the increase of the device operating frequency.To obtain excellent output power density at higher operating frequency,it is necessary to reduce the external impedance of the device and make full use of the voltage and current swing.The working state of the device tends to be nonlinear,the output power density decreases,and the external impedance decreases.When the device is close to the nonlinear state,it is necessary to reduce the external load impedance of the device to obtain the excellent output power density in this state.(4)The microwave power characteristics of AlGaN/GaN HEMT devices were studied by adjusting the field plate structure and groove depth.The parasitic effect of the source field plate is small and the dynamic load line is narrow.The output power density of the device can be further improved by further improving the device leakage swing utilization rate.The Pout of the source field plate structure device is 12.6W/mm@10 GHz,which is 20%higher than that of the grid field plate.With the increase of the groove depth,the capacitance characteristics of the device are significant,the gate voltage swing decreases,the dynamic load line widens,and the output power decreases.The output power density of fluted gate devices can be further improved by increasing the gate pressure swing.In summary,by studying the influence of the structural changes of the device on the dynamic load line and microwave power characteristics of the device,a research idea on how to improve the output power density of the device at high frequency is proposed,which is the basis for the subsequent analysis of the microwave power characteristics of gallium nitride devices.The research provides a theoretical basis.