Electro-thermal-mechanical Analysis And Failure Investigation Of AlGaN/GaN HEMTs Under High Power Microwave (HPM) Pulses

During the last few years,AlGaN/GaN high-electron mobility transistors(HEMT)has drawn great interest for the excellent RF performance.It has outstanding material advantages such as the high sheet charge density of two-dimensional electron gas(2-DEG)at the hetero-structure,the high carrier mobility and saturation velocity in the channel,and the large breakdown voltage owing to the GaN material.In this article,electro-thermo-mechanical results of a typical field-plate(FP)AlGaN/GaN high electron mobility transistors(HEMT)are fully presented.We characterize the thermal and stress results of the power device by self-consistent electro-thermal TCAD simulation and own code in finite element method respectively.Firstly,special attention was paid to the structure model and materials element of AlGaN/GaN HEMTs,which was respectively determined from scanning electron microscope(SEM)cross-section images and spectrum analysis.Secondly,in order to account for the high density 2-DEG as a result of spontaneous and piezoelectric polarization effects,a polarization model can be used in the TCAD models.Low field mobility model,which is also the function of lattice temperature,the Shockley-Read-Hall carrier generation-recombination model and the lattice heating model were selected to simulate the power device.Eventually,a set of fundamental semiconductor equations,such as Poisson's equation,continuity equation,transport equation,and lattice heat flow equation were solved using finite element method.In addition,analytically thermal destruction temperature has been calculated based on the measured destruction power in the experiment under different pulse durations.The temperature evolution over pulses,and the calculation of thermal resistance and capacitance used in this theoretical model will be exhibited in an analytic method.Furthermore,TCAD simulation is used to calculate the transient temperature in comparison with the theoretical results mentioned above.Eventually,transient stress and stress profiles can be calculated using our own code with finite element method(FEM).Temperature and stress profiles of the AlGaN/GaN HEMTs are presented in order to get insight into possible mechanisms leading to breakdown of the device.