Research On Device Physics And Modeling Of GaN-on-Si High-electron Mobility Transistors

Model is a tool for simulating the electrical characteristics of a device,a bridge between circuit engineers and device,and plays a key role in circuit design and development.An accurate model can assist circuit engineers in predicting circuit performance parameters with high accuracy in circuit design,which can improve the success rate of circuit design,shorten circuit development cycles,and reduce development costs.However,the current mainstream GaN HEMT device models are mostly empirical models based on device measurement data,which are not able to predict complex non-ideal effects of devices.Especially in the circuit simulation platform,it is impossible to predict the threshold voltage instability,on-resistance change and current collapse of GaN HEMT device under different frequencies and different drain-source voltage in the power conversion circuit,which cannot meet the the design requirements of the rapid development of GaN monolithic IC.Therefore,this thesis explores the GaN physics based model and model library technology that based on the intrinsic physical properties of GaN HEMT device.It can predict the characteristics of GaN-on-Si HEMT devices under different drain-source voltage and switching frequency,which is suitable for Cadence and ADS circuit simulation platform.The GaN-on-Si HEMT device model library provides guidance for all-GaN IC design.The main research contents of thesis are as follows:(1)Research on physical base model of GaN-on-Si HEMT device.Firstly,the effects of the Al GaN/GaN interface trap center and the GaN buffer buffer layer bulk trap center on the threshold voltage and on-resistance of device are researched by using TCAD software Sentaurus.Qualitative analysis of the trap center and the change of device characteristics is made to provide reference for subsequent parameter modification of modeling.Secondly,the indirect recombination theory of semiconductor carrier and Schrodinger Poisson equations are innovatively combined in this thesis.The physical basis calculation models for threshold voltage,two-dimensional electron gas in the draingate access region and drain current of GaN-on-Si HEMT device under different drainsource voltages and switching frequencies are established.(2)Research on model parameter extraction technology and model library establishment technology of GaN-on-Si HEMT device.Based on the physical model of GaN-on-Si HEMT device established above,the transfer characteristics and output characteristics of GaN-on-Si HEMT commercial device EPC 2007 C were tested under different off-state drain-source voltages and different switching frequencies.Based on a model parameter extraction method for GaN-on-Si HEMT device proposed in this thesis,the model parameter extraction,fitting and establishment are carried out.The model has high predictability,which verifies the correctness of the model established in this thesis.Secondly,based on the domestic GaN device technology platform,the construction of GaN-on-Si HEMT device model library suitable for Cadence and ADS simulation platform,including enhanced GaN logic device,depletion GaN logic device and enhanced GaN power device is carried out.The fitting accuracy of the model library to the device threshold voltage,on-resistance,transfer characteristics and output characteristics is not less than 0.86.