Semiconductor Devices With High Performance Based On Piezotronics

The wide bandgap semiconductor crystal structures represented by gallium nitride and zinc oxide exhibit central asymmetry.Piezotronics devices use these piezoelectric semiconductors to generate polarization charges under stress and strain conditions,and regulate carrier transport,recombination,separation and other processes in the depletion region,and develop a series of ultra-high sensitivity strain sensors.The junction polarization charge regulation provides a new method and means for the study of stress-strain coupling regulation in third-generation semiconductors,and has received widespread attention in theoretical,experimental,and application fields.However,it is still difficult for mature devices to consider the design of piezoelectric polarization charges in the junction region,and there is a huge challenge to the flexible manipulation means in micro and nano scales.After device preparation,flexible control of junction polarization charges through external manipulation has become an easy means to achieve at present.However,from the physical basis of semiconductor devices,a systematic explanation of the regulation mechanism of piezotronics still needs to be improved.In this dissertation,based on the basic structure of piezoelectric semiconductor devices,the influence of the piezoelectric field regulation in the junction region of piezotronics devices is studied,and the piezoelectric bipolar transistor and piezoelectric avalanche transistor models with high sensitivity are proposed.The influence of the piezoelectric polarization field on the response time and subthreshold swing parameters of piezotronics devices is studied,this dissertation enriches and perfects the theory used in the design and research of high-performance piezotronics devices.The main research contents and results of this dissertation are as follows:1.The mechanism of balance regulation and tunneling effect regulation in the junction region by the piezoelectric polarization field is studied,and the mechanism of avalanche breakdown process regulation by the piezoelectric polarization field in the junction region is also studied;For metal semiconductor contact structures under different bias conditions and composed of different materials,diffusion theory,hot electron emission theory and hot field emission theory are used to study the control mechanism of piezoelectric polarization field,and a theoretical model of polarization controlled avalanche diode is proposed.2.Based on the classical semiconductor physics,a piezotronic bipolar transistor model is proposed.Combining the current gain characteristics of the bipolar transistor itself,the electrical performance,dynamic characteristics,carrier transport behavior,etc.of the device are calculated by finite element simulation.The performance of the device can be significantly improved by the piezoelectric polarization field.As a multi junction device used as a mechanical sensor,the sensitivity factor of the piezotronic device can reach more than 10~4.And this principle can be used for more junction cascade amplification situations such as Darlington devices,and the sensitivity will be further greatly improved.3.As a typical nonlinear amplification mechanism within the junction area,based on the avalanche breakdown mechanism of PN junction reverse bias,combined with the regulation of piezoelectric polarization field in the junction area,a piezotronic avalanche transistor device model is proposed.On the basis of the current multiplication effect of avalanche breakdown,the sensitivity factor of piezotronic avalanche devices when used as mechanical sensors can reach 10~6～10~7.The electrical output characteristics of the device are calculated using the finite element method.The piezoelectric polarization field can effectively adjust the avalanche multiplication process.The sensitivity factor of the finite element calculation can reach 1.2×10~6 provides a new approach and method for designing ultra-high sensitivity piezotronic semiconductor devices.4.The influence of piezoelectric polarization field on the important parameters of device performance,such as response speed,subthreshold swing,etc.For switching devices based on PN junction,the piezotronic polarization field can effectively shorten the switching response time.The theoretical calculation results show that when the strain state is switched from-2%to 2%,the switching response time is reduced by 50 times.The piezoelectric polarization field can effectively regulate the subthreshold swing of devices in different device structures.For the MOSFET,the subthreshold swing of piezotronic regulation can be optimized from 67 m V/dec to 15 m V/dec;For impact ionization field-effect transistors,the subthreshold swing can be optimized from 0.52m V/dec to 0.37 m V/dec.This study has theoretical guidance significance for ultra-fast,ultra-high sensitivity piezoelectric and piezoelectric optoelectronic strain sensors.Based on the above research results,high performance piezotronic devices can effectively improve the current bottleneck problems in semiconductor devices,and have potential important applications and scientific value in cutting-edge fields such as current signal amplification,small strain detection,optoelectronic detection systems,and high-speed switches in the future.