The Study Of Trapping Effect And Characterization Technique Of GaN Based Hemts

Ga N-based microwave power devices have advantages of high operating voltage,high frequency,and high temperature resistance,and have become the key device in the fields of radar and 5G communications.With the continuous breakthrough and improvement of device design technology and manufacturing technology,its performance and electrical parameters still be limited by the degradation under longworking time,collision with gamma irradiation in the near-Earth space,and low heat dissipation efficiency.Trapping effect has been proved playing an important role in leading to the degradation and failure of Ga N-based devices.This work has conducted in-depth research and discussion on the method of characterizing traps' parameters based on the current-transient response.Contents include the change of defects and traps under electrical stresses,optical pulses and high-energy partical irradiation for Ga N HEMTs,and the degradation of electrical parameters and the physical damage mechanism.They also include the effect of the electrical parameter on the thermal measurement and the contribution of 2DEG to the horizontal thermal transport.The main contents are as follows:1)The theoretical system for characterizing device trap parameters by current-transient method has been improved,and a new method of constructing traptime-constant spectrum based on Bayesian deconvolution is proposed.Theconstruction of time constant spectrum is the most important step and coremeans to extract trap information from the current-transient response.Itstraditional construction way has the disadvantages of insufficient peakaccuracy,ripples in non-characteristic regions,and discontinuous spectralvalues.This Bayesian deconvolution-based technique solves these problemsand provides a new way for researchers.In addition,a new concept foraccurately characterizing the effect of the trap on the output current of thedevice,that is,the differential amplitude spectrum,has been proposed.Itcompensates for the inherent shortcomings of the time constant spectrum insolving the trap amplitude problem,and helps enrich the paths of current-transient method.2)Some special behaviors of current-transient response,such as non-monotonictransient current response,are predicted theoretically and tested in experiments.Solved the problem that one phenomenon may correspond to multiple physicalmechanisms,that is,it is given whether the trap-transient response is a captureprocess of electron trap or release process of a hole trap,and provided a newway to locate the trap spatial position.Using the nature of the current-transientresponse,that is the change in 2DEG,and the channel resistance,a voltage-transient response has been proposed.It resolves the errors caused by the"voltage drift" phenomenon that exists when collecting current-transientresponses.The problem further enriches this theoretical system forcharacterizing device trap effects.3)Proposed and improved a dynamic model to explain the PPC phenomenon inGa N-based devices represented by Al Ga N / Ga N heterojunctions.Predictedentire process of the output current rise and decay of the device under 400-nmlight for the first time.It has been verified experimentally.For the first time,aphenomenon that a part of current is out of gate's control caused by ?-rays wasreported.The electrical and optical methods were used together to determineits failure mechanism.Its generation and disappearance processes wereobserved.This further improved the radiation-resistant design of Ga N-baseddevices.4)Verified that there is an error caused by the test current when using the lineartemperature-sensitive characteristic of the Schottky junction forward junctionvoltage to measure the temperature-transient response of the active region ofthe device,and proposed a method for compensating the total thermalresistance calculation.The steps to further optimize the testing process havebeen given.An Al Ga N/Ga N heterojunction sample that separated the heatingzone and the measurement zone was designed to study the effect of 2DEG onthe horizontal heat transfer performance of the device.The temperature delaycaused by 2DEG was observed,which proved that 2DEG has an auxiliary rolein this process.This work systematically studies the trap effect in Ga N-based HEMT devices,improving the transient current characterization technique,explaining some special transient current manifestations,and further improves the device trap characterization.In addition,the thesis also studies the influence of electrical parameter changes on electrical temperature measurement and the lateral heat transfer characteristics of the device.Research results make great sense for improving the reliability of Ga N HEMTs.