Research On Kink Phenomenon And Dynamic Resistance Characteristics Of GaN-Based HEMT

Due to the excellent properties of gallium nitride material,such as wide bandgap width,high breakdown electric field,high electron mobility,strong radiation resistance,GaN-based electronic devices are very suitable for application in extreme condition of high frequency?high voltage and high power.Such as AlGaN/GaN heterostructure high electron mobility transistors?HEMT?,in the new energy vehicles,5G communication,laser and radar,and other industries have important application prospects.However,GaN-based HEMT devices are faced with serious electrical reliability problems,such as high temperature degradation effect,gate and drain delay effect,kink effect and dynamic resistance enhancement effect,which are not conducive to their large scale commercial applications.In this context,it has very important social application values to analyze several related key reliability problems and reveal the physical mechanism behind those problems.Firstly,the current research status and existing problems of GaN-based HEMT are described in this thesis.Then,we introduce the basic properties of GaN materials,the structure and working principle of the device.Finally,the important parameters characterizing the device performance are summarized.The main research contents of this paper can be summarized as follows:1?Research on the variable temperature characteristics of AlGaN/GaN HEMT.The results show that with the increase of temperature,the dominant factor of device degradation is not the decrease of two-dimensional electron gas with temperature,but the increase of square resistance with temperature.The square resistance is determined by the 2DEG concentration and mobility of the device.Therefore,the experimental extraction and theoretical calculation of the 2DEG mobility of the device are carried out.It is found that the electron mobility limited by the polar optical phonon scattering mechanism decreases exponentially with the increase of temperature,which is the main reason for the increase of the square resistance and the degradation of the device under high temperature.2?AlGaN/GaN HEMT kink effect is studied.Under different drain bias,the kink degrees of the two scans are significantly different.Through the gate bias experiment,it is observed that the kink degree is alleviated in the open state,increased in the semi-open state,and unchanged in the closed state.The kink effect caused by reverse gate current is not significant.Combined with the theory of semiconductor physics,it's proposed that kink effect of devices is mainly caused by the electron capture and thermion-assisted electron detrapped by donor-like deep level defect state in GaN buffer layer.3?Study on the dynamic resistance characteristics of lattice matched In_0.17Al_0.83N/GaN HEMT.We built a test system for hard and soft switching model and study the dynamic resistance characteristics of lattice-matched In_0.17Al_0.83N/GaN HEMT devices under different switching models.It's found that the increase of dynamic resistance in hard switching model is due to the virtual gate effect caused by surface state trapping electrons.With the increase of drain bias stress in the off-state,the dynamic resistance decreases and then increases slightly,which is due to the detrapping and trapping effect of electrons in the buffer layer.Under the soft switching model,it is verified that the defective state in InAlN is donor-like state,and the stability time is helpful for the recovery of the dynamic resistance.