Research On Electrial Performace Of Two-Dimensional Electron Gas In ZnMgO/ZnO Heterostructure

ZnO is a preferred material following the III-nitride to develop the high frequency, high power and high temperature microelectronic devices. This material has received widespread attention owing to its superior electrical performance such as wide band gap, high saturated electron drift velocity and high breakdown field strength. Polarization electric field caused by the spontaneous polarization and piezoelectric polarization, can induce high-concentration polarization charge at the ZnMgO-ZnO interface. The polarization charge can modulate the energy band of the heterostructure, and further affecting the performance of the related devices. The electron and scattering center can be separated spatially by introducing the modulation-doping and one space layer, thereby greatly enhancing the concertration and mobility of two-dimensional electron gas(2DEG) in the ZnO channel layer.Despite of some transport experimental reports about the 2DEG in ZnMgO/ZnO heterostructures, the theoretical study is little, especially the study about the impacting of the strain relaxation and the modulation-doping on the properties of the 2DEG, which seriously affected the understanding of the ZnMgO/ZnO heterostructure, and the research and development of ZnO-related electronic devices. The influence of the modulation-doping and the of strain relaxation were investigated separately. The main results as follows:1. Base on the model of modulation-doped ZnMgO/ZnO heterostructure, we study the distribution and the sheet concentration of the 2DEG in heterointerface for different structural parameters by solving the one-dimensional Poisson and Schr?dinger equations self-consistently. The influence of the doping concentration and the spacer layer were investigated separately. The computational results indicate that the 2DEG in the channel layer consists of the electrons induced by the polarization effect and the electrons supplied by the doping layer, and thus can be controlled effectively by changing the thickness of the spacer layer and the doping concentration.2. Based on the model of undoped ZnMgO/ZnO heterostructure with relaxation-dependent piezoelectric polarization, we study the distribution and the sheet concentration of the 2DEG in heterointerface for different structural parameters by solving the one-dimensional Poisson and Schr?dinger equations self-consistently. The influence of the thickness of ZnMgO barrier, the Mg content and the degree of strain relaxation were investigated separately, and the corresponding results were analyzed by concerning the polarization and the band offset. The computational results indicated that the polarization can be changed by altering the Mg content and the degree of strain relaxation, and thus the 2DEG can be controlled effectively.