Design And Research Of New High Energy Efficiency P-GaN Buried AlGaN/GaN HEMT

AlGaN/GaN HEMTs have become the hot spot in the research of GaN-based power semiconductor devices due to their superior device performance and relatively mature technology,and they have been widely used in wireless communications,aerospace,and other fields.At present,the research of AlGaN/GaN HEMT mostly focuses on high withstand voltage,high working frequency band,high output power,etc.,but high energy efficiency research is rarely involved.However,with the promotion of the concept of strengthening energy saving and reducing consumption and promoting green development,the importance of improving the energy conversion efficiency of devices has become increasingly prominent.In this context,focusing on improving device energy efficiency,AlGaN/GaN HEMT device design,power added efficiency（PAE）improvement,and structural optimization have been studied in this thesis.The main research work and results are as follows:First of all,the electrical characteristics of AlGaN/GaN HEMT（PBL GaN HEMT）with P-type GaN buried layer are analyzed and studied in this thesis.In this structure,the P-type GaN buried layer is introduced into the buffer layer under the gate.The buried layer and the N-type GaN buffer layer form a PN junction,which depletes the two-dimensional electron gas concentration under the gate and increases the threshold voltage and breakdown voltage.The channel carrier mobility is increased,which improves the device transconductance.The product of the two-dimensional electron gas concentration and mobility is reduced,and the saturation drain current density of the device is slightly reduced.The width of the depletion region under the gate of the device is increased,which reduces the gate-source capacitance.Compared with conventional devices,the cut-off frequency and maximum oscillation frequency of this structure are increased by 23.53%and 37.47%,respectively.Then,the influence of the key characteristic parameters of AlGaN/GaN HEMT on its power added efficiency is simulated.The analysis shows that the positive shift of the threshold voltage,the increase of the transconductance and the decrease of the gate-source capacitance will improve the power-added efficiency of the device.Through simulation,it is found that compared with conventional GaN HEMT,the output power and power added efficiency of PBL GaN HEMT are improved.As the operating frequency increases,the power-added efficiency of conventional GaN HEMT devices decreases,and the power-added efficiency of PBL GaN HEMT devices first increases and then decreases.In the entire frequency simulation range,the PBL GaN HEMT has a significant improvement in the power-added efficiency in the S-band and below,and the improvement in the S-band is the most significant.Then,through simulation,the influence of the doping concentration D_PBL of the P-type buried layer and the distance from the buried layer to the Al GaN barrier layer N_{a PBL} on the power-added efficiency of the device is discussed.Studies have shown that the doping concentration of the buried layer and the distance from the buried layer to the barrier layer have relatively independent effects on the power-added efficiency of the device,and both have optimal values.When the operating frequency is 2.4 GHz,the P-type buried layer parameters are D_PBL=0.2μm and N_{a PBL}=4.0×10¹⁷ cm^-3,the PBL GaN HEMT device obtains the maximum PAE of 73.50%,compared with conventional GaN HEMT,this is an increase of 32.82%.Finally,based on the PBL GaN HEMT structure,a GaN HEMT（HDP GaN HEMT）structure with a horizontal double P-GaN buried layer is proposed,and its electrical characteristics are simulated.Through optimization,the influence of the thickness t _RP,the doping concentration N_{a RP} and the distance D_RP from the barrier layer of the buried layer on the right on the power-added efficiency of the device is discussed.By introducing the double buried layer,the horizontal PN junction formed between the vertical PN junction formed by the buried layer on the right side and the GaN buffer layer and the horizontal buried layer is increased,which reduces the channel electron concentration and greatly improves the electron mobility.The saturation drain current density of the device increases,and the transconductance further increases.The depletion effect is enhanced,and the gate-source capacitance is further reduced.The doping concentration of the buried layer on the right and the distance to the barrier layer have relatively independent effects on the power-added efficiency of the device,and both have optimal values.When the operating frequency is 2.4GHz,D_RP=0.2μm,N_{a RP}=4.0×10¹⁷ cm^-3,the device obtains the maximum PAE of 76.83%,which is an increase of 38.83%compared with conventional GaN HEMT.The smaller the thickness of the buried layer on the right,the better the threshold voltage,transconductance,and gate-source capacitance characteristics of the device,which helps to improve the PAE.Through the design of the device structure,the simulation analysis of characteristic parameters and the optimization simulation and analysis of the key structural parameters of the device,it can be known that the device structure and working conditions together affect the PAE.Adding the P-type region to the buffer layer effectively increases the threshold voltage and transconductance of the device,reduces the gate-source capacitance,thereby improves the PAE of the device,and this thesis provides experience and ideas for the design of the device to improve the PAE.