Research On Irradiation Failure Mechanism And Reliability Of GaN-on-Si Power Devices

As an essential component of electronic equipment,the performance requirements of power electronic devices are more and more stringent with the development of space technology.Compared with traditional silicon-based MOSFET devices,GaN power devices have emerged as promising candidates for power applications at high frequency,high temperature,high electric field and other harsh environments.Combined with the strong radiation tolerant of GaN materials,Si-based GaN power devices have a wide range of applications in space vehicles such as satellites and spacecraft.Due to the complexity of the space irradiation environment and the reliability of Si-based GaN power devices,the characteristics of radiation-tolerant are greatly challenged.Therefore,it is extremely important to understand the radiation effects in Si-based GaN devices.In view of the above background,this work researches on the radiation impact on Si-based GaN power devices.The degradation mechanisms of GaN devices is revealed by analysing the change of the electrical performance caused by radiation effect.Then,we can promote the anti-radiation reinforcement of GaN devices based on the theoretical achievements.The main research contents are as follows:?1?The effect of ⁶⁰Co gamma irradiation on the static characteristics of D-mode Si-based GaN power device are investigated experimentally.It was found that within 2Mrad dose,the sub-threshold swing of the GaN device was reduced by more than 20%.The change of interface charge caused by gamma irradiation was studied by C-V characteristic testing method.The results show that LPCVD-SiN_x/AlGaN interface is more susceptible to irradiation effect than AlGaN/GaN heterojunction structure.In addition,low dose irradiation can improve the quality of SiN_x/AlGaN interface and reduce the interface charge density.?2?The total dose effect of ⁶⁰Co gamma irradiation on the characteristics of commercial E-mode GaN devices are studied in detail.In order to simulate the actual working environment of devices in space,the devices were radiated under voltages stress.The results show that the threshold voltage and leakage current of the commercial enhanced GaN device have a small change range within 1.5Mrad irradiation dose,and the AlGaN/GaN HEMT devices have a good anti-irradiation property to gamma irradiation.?3?The effects of the electron irradiation on AlGaN/GaN HEMT devices are researched experimentally.The normally-off AlGaN/GaN HEMT with P-GaN gate was radiated under three different stress conditions which are GND-State?three-terminal grounded?,OFF-State?gate turned off?and ON-State?2DEG channel turned on?.The results show that under the condition of large forward gate stress,the gate of GaN devices are seriously degraded by the irradiation dose above 500Krad.Combined with the results of the stress effect on GaN device,it is found that electron irradiation can intensify the effect of forward gate stress.Applying a large bias stress over the gate result in a high electric field in the depletion region of the P-GaN layer is the main reason of converting Schottky-type gate into the ohmic-like gate and final gate breakdown.On the contrary,the DC characteristic parameters of GaN devices on the other two conditions within the1.8Mrad dose have a great recovery after 24 hours at room temperature.The results show that the electron irradiation effect causes the impermanent damage to GaN devices when the three terminals are grounded or the gate is turned off.The N vacancy was induced by the 1MeV electron irradiation as the donor defect in the passivation layer and the point defect produced by the elastic collision between electrons and atoms in the material forms a leakage channel.