Research On Single Event Burnout Mechanism Of Nitride HEMT And Aerospace Devices

Nitride wide band-gap semiconductor devices have advantages of high breakdown,low on-resistance,low parasitic capacitance,high switching frequency,etc.It has been widely used in the field of fast charging,and has shown great potential in electric vehicles,industrial motors,aerospace power supplies and other fields.With the development of aerospace technology,space environment spacecraft and satellite detection equipment has put forward higher requirements for the power system.The nitride HEMT（High Electron Mobility Transistor）as the core component of the power supply module shows the advantages of high efficiency,low switching loss,high temperature resistance,and small size,which can meet the demands of aerospace power systems.However,device failure caused by single particle irradiation severely limits the application and development of GaN-based devices in aerospace.Furthermore,AlGaN belonging to GaN material system have stronger breakdown voltage and higher temperature performance,and better characteristics under harsh conditions such as irradiation.Therefore,the development of AlGaN-based semiconductor materials provides a new method to solve the problem of single event effect in the aerospace application.Systematic studies and the effect of single event are carried out from a theoretical and experimental perspective in this paper,focusing on the characteristics of single event and the basis of the hardening technology of devices.A novel AlGaN channel HEMT is developed to improve the performances of channel mobility and FOM.Based on the experimental performance and numerical model,the single event burnout and the hardening mechanism of nitride channel devices have been proposed.The relevant achievements can lay the foundation for the further application of the nitride semiconductor in aerospace irradiation.The achievements of main research results are as follows:1.In this paper,we systematically study and reveal the irradiation process for heavy particles of Ta(2006.4 Me V,LET=75.4 Me V·mg^-1·cm²)and the failure mechanism of single event burnout of p-GaN gate HEMT with GaN channel on Si substrate.The research contents include in-depth evaluation of the experimental performance of single particle burnout,characterization of the performance degradation after irradiation,establishment of a double-pulse switching circuit system to measure the dynamic circuit parameters of the device,and analysis of the single particle burnout process based on the microstructure.The results show that the p GaN HEMT can obtain a burnout voltage range of 350～400 V under high-energy heavy particle irradiation（Voltage applied to the drain has a step of 50 V）,and the performance is at the advanced level of the international reports.If the single event burnout occurs in off-state of the high voltage,HEMT will lose the gate control and transconductance,which will cause the abnormal value of gate transfer characteristic,gate and off-state leakage,capacitance of the gate-source and gate-drain.If HEMT is irradiated but no single event burnout,the on-resistance,device capacitance and Schottky depletion performances will degrade to varying degrees.After the irradiation with high-energy heavy particle of Ta,the switching time of p GaN gate HEMTs with GaN channel will be increased,resulting in more switching energy loss.When single event burnout occurs,a heat point will be generated near the drain area,causing the drain metal or semiconductor material to burst and form a cavity.The distribution of high-energy incident particles of Ta was captured directly inside the HEMT with burnt-out failure for the first time,and the concentration was higher in the cavity center,which also indicates that the failure cavity region is the direct evidence caused by single event burnout.2.Based on the novel design of structure GaN/Al_0.4Ga_0.6N/AlN/Al_0.1Ga_0.9N/C-Al_0.1Ga_0.9N,Al_0.1Ga_0.9N channel HEMT with Si substrate has been designed and manufactured.The square resistance of 883Ω/□,the contact resistance of 1.29Ω·mm,the 2DEG density of 1.29×10¹³ cm^-2 and the field effect peak mobility of 405 cm²/V·s was obtained.The trap state density of 0.16-4.80×10¹³ cm^-2e V^-1,the time constant of 4.46-14.55μs,and the corresponding activation energy of 0.354 e V-0.385 e V was measured and calculated by frequency-dependent capacitance and conductance.This paper proposed a novel vertical Ohmic/Schottky hybrid drain structure,which can reduce the specific on-resistance R_ON,SPby 11.9%and improve the FOM by 13.5%compared with the traditional hybrid drain HEMT with the gate-drain spacing of 21μm,indicating that it has the ability to optimize and control the power characteristics,and the mechanism for the improved performance was analyzed.The HEMT finally achieved a breakdown voltage of 1730 V and a FOM of 219MW/cm²,providing the basis for the development of single event hardening devices.3.In order to solve the problem of alloy disordered scattering of Al_0.1Ga_0.9N channel HEMT on Si substrate,a novel structure of superlattice channel is proposed and manufacture,that is,a GaN/AlN structure with 20 layers of cycle and unit period of 5/1 nm is designed as the channel layer of AlGaN HEMT.The maximum field effect mobility of 510 cm²/V·s was obtained for the superlattice channel equivalent to 20%Alcomponent,which achieved the best mobility performance in the AlGaN channel HEMTs on silicon substrate.When the gate-drain spacing is 8μm,high breakdown voltage of 670 V along with a maximum output current of 196 m A/mm,and an ON/OFF ratio of over 10⁷ was achieved in the novel HEMT.Compared with Al_0.1Ga_0.9N channel material,the trap state density is lower,thus reducing the channel scattering and collision.The evolution mechanism for trap state of superlattice channel HEMT has been investigated based on gamma irradiation.The results show that the negative shift of threshold voltage is mainly caused by hole trapping effect at the barrier layer or the interface between the barrier and the channel layer.The lower channel will induce new trap states under the irradiation to compensate the channel electrons,and these possible mechanisms will affect the density and time constant parameters of trap state in the channel after irradiation.4.The carrier motion mechanism of the HEMT after heavy particle incident has been deeply analyzed based on the experimental basis and single event burnout model of the enhanced p GaN gate nitride channel HEMT,and the single event burnout mechanism of electric-temperature coupling and hole injection in the gate is innovatively proposed.At the moment of single event burnout,the high electric field peak will quickly transfer from the gate side to the source and the drain side.The concentration of carrier and electric field distribution are dynamic changing processes.The electric field acceleration of carriers will cause the lattice temperature to rise,resulting in the lattice-temperature mainly concentrated around the drain side region,including the drain,the passivation layer,AlGaN/p GaN heterojunction.The mechanism of gate injection holes based on back-channel is that,after electrons flow to the drain under high electric field,a large number of high-concentration holes are left in the channel layer or the buffer layer,and these will be injected into the gate with low potential,resulting in a sharp increase in the gate current of the HEMT and thus burning out.Both mechanisms may exist in the single event burnout process,that is,the movement of electron-hole pair will produce the high-peak electric field after heavy particle incident,and coupled to the lattice peak temperature concentration region,will cause single event burnout of the HEMT.In the form of device explosion due to the high temperature or avalanche breakdown with the sharp rise of current,the phenomenon is basically consistent with the experimental conclusion of Ta particle incident.At the same time,the technology of the AlGaN channel HEMT can increase the single event burnout voltage by up to 50%,which provides a valuable novel theoretical basis and the reinforcement method for the aerospace irradiation of single event burnout.