Study Of Radiation Effects Of GaN-based HEMTs

GaN-based high electron mobility transistor(HEMT)has been widely used in satellite communication,space station and other fields due to its high thermal conductance,high breakdown voltage and radiation resistance.However,the existence of a large number of high-energy particles in space will introduce defects in the device,resulting in the performance degradation or even failure of the device,which seriously threatens the reliability of the device.Therefore,it is of great significance to further study the radiation damage mechanisms of AlGaN/GaN HEMT to improve the reliability of spacecrafts and satellites.In the dissertation,the radiation effects of AlGaN/GaN HEMT have been systematically studied by combining experiment and simulation.Through analysis of the output of radiation,degradation mechanism is revealed,which is of guiding significance for the radiation hardening of devices.The main research contents are as follows:Firstly,the basic principles of AlGaN/GaN HEMT were analyzed,and a two-dimensional electronic gas charge control model was established.Based on the radiation environment and radiation effect,the radiation damage mechanism of the GaN material and AlGaN/GaN HEMT was analyzed.The radiation induced defects are the main mechanism of the radiation damage.Secondly,the total dose effects of ⁶⁰Co gamma radiation of AlGaN/GaN HEMT was studied.First of all,AlGaN/GaN HEMT devices were radiated by non-electrified?radiation to simulate the device's radiated state in the non-working state.It is found that,contrary to the results of previous studies that the performance of the device was degraded seriously after?radiation,the electrical performance of the non-electrified device is improved after?radiation,which is due to the introduction of a small number of acceptor defects under the gate.Then,the radiation characteristics of the device under the condition of on-line irradiation simulation were studied.It is found that the electrical characteristics of the device degrade greatly after electrified on irradiation.In order to explore whether the degradation is caused by radiation or by electrical stress,the open state constant electrical stress experiment was carried out.Through comparative analysis of experimental results,it is believed that radiation aggravates the electrical stress effect of the device.Finally,the proton of different energies and doses used to radiate AlGaN/GaN HEMT was studied.The results show that low energy or high dose proton injection can cause serious degradation of the device.This is because the non-ionizing energy loss passed from low-energy protons to lattice atoms is larger.Combined with simulation software SRIM,the interaction between protons and GaN materials was simulated,including the stopping positions,induced vacancy distribution and energy transfer of protons in the GaN material.And the vacancy density generated by protons at different depths of AlGaN/GaN HEMT was calculated.It is found that Ga vacancy is the main defect in Al GaN layer and GaN layer and the main factor that leads to device degradation.In addition,according to the degradation mechanisms of AlGaN/GaN HEMT devices under different radiation conditions,some radiation hardening methods are proposed from aspects of device technology,material and structure.