Design And Simulation Of Power GaN HEMT With High Efficiency-energy

As the third generation wide band gap semiconductor material,gallium nitride?GaN?has high electron saturated velocity,high breakdown voltage,high radiation tolerance and excellent heat resistance.In comparison with the traditional Si and GaAs material,these superior characteristics with GaN material make GaN can be used in large power density,high temperature and high frequency field without limitations like Si or GaAs.Simultaneously,due to a great advantage of the power quality factor for GaN material,AlGaN/GaN high electron mobility transistor?HEMT?,a kind of GaN device,possesses a broader development prospect for microwave high power applications.With the development of wireless communication system,phased array radar and aerospace fields requiring the microwave power amplifier with higher and higher performance,mostly ways in achieving the high efficiency output target are based on the control of the external circuit to the power tube and the use of compensation.It is rare for the special requirements on the internal parameters of the device to research the power-added efficiency from the chip level.Today,the development and application of high efficiency-energy GaN HEMT have a great potential in uprating the performance of the amplifier and reducing the power consumption under call of“Energy conservation,Emission reduction,green and efficient”.So,the high efficiency-energy GaN HEMT is well worth doing research and analysis.The paper is written in this context.In order to study the reason that affects the power added efficiency?PAE?,the external factors and the internal parameters of the chip are analyzed respectively to obtain the methods and ideas of designing the high efficiency-energy GaN HEMT.The results indicate that although the PAE of the chip is restricted by the external operating conditions and the forms of matching,the essential elements are contributed to the capacitance and the output impedance of the chip.In the simulation of internal parameters of the chip to the PAE,it is found that the peak transconductance of the device can be slightly reduced in exchange for a wider flat area of transconductance,which can be improved the efficiency output ability of the chip.The optimized transconductance parameter simulation results show that the PAE is increased from 67.3%to 82.3%.Meanwhile,the reduction of the gate-drain/gate-source capacitance is also benefit to enhancing the output capability of the chip with high power and high efficiency.On the basis of the above research on improving the efficiency output of the chip,a novel structure of GaN HEMT?DRBL GaN HEMT?which has double recessed barrier layer is designed and proposed in this paper.The simulation results indicate that the growth rate of drain saturation current is weakened,the peak transconductance is reduced and the saturation region of transconductance is extended due to the double recessed barrier layer structure.The recessed gate-drain barrier layer reduces the electric field crowding at the gate corner near the drain and increases the breakdown voltage.Further investigation shows that double recessed barrier layer beside of gate reduce the depletion layer extension to source/drain effectively.It leads to the decrease of the gate-source and gate-drain parasitic capacitance.Compared to the conventional structure,the transconductance saturation region of DRBL GaN HEMT is increased by 0.5 V,the breakdown voltage is increased by 8.7%,and the gate-drain/gate-source capacitance are decreased by 6.3%and11.3%,respectively.The simulated small-signal high frequency characteristics of DRBL GaN HEMT show that the RF characteristics are improved.The maximum oscillation frequency for DRBL GaN HEMT is increased from 57GHz to 64GHz and the power gain is increased by 1dB.The superior characteristics with DRBL GaN HEMT make it having the greater output potential at high power high efficiency.The large signal characteristics of DRBL GaN HEMT are also verified by simulation.DRBL GaN HEMT has the same saturation power density 8.7W/mm and 6.9W/mm as the conventional structure at 600MHz and 1200MHz,respectively.However,due to the smaller DC power consumption,DRBL GaN HEMT has the higher PAE compared to the conventional structure.The simulations show that the maximum PAE for DRBL is 90.2%at 600MHz,88%at 1200MHz when V_gs=-4V,V_ds=20V.As the operation frequency increased to S band 2400MHz,DRBL GaN HEMT begins to show the high efficiency-energy output characteristic.It can be attributed to the smaller gate-drain and gate-source capacitance.The saturation power density achieves to 6.4W/mm and the maximum PAE achieves to 83.8%at 2400MHz for DRBL GaN HEMT.Both are higher than the 5.0W/mm and 80.3%for the convention GaN HEMT.All the results show that the advantages and the potential capacities of DRBL GaN HEMT at high efficiency-energy are greater than the convention GaN HEMT.