基于低温硅技术的赝晶SiGe应变弛豫机理

Strain relaxation mechanism of pseudomorphic SiGe using low-temperature technology

基于能量平衡条件,结合低温硅(LT-Si)剪切模量小于SiGe的实验结果,从螺位错形成模型出发,给出了基于LT-Si技术的赝晶SiGe应变弛豫机理.该机理指出,赝晶SiGe薄膜厚度小于位错形成临界厚度,可通过LT-Si缓冲层中形成位错释放应变;等于与大于临界厚度,位错在LT-Si层中优先形成,和文献报道中已观察到的实验结果相符合.同时,实验制备了基于LT-Si技术的弛豫Si0.8Ge0.2虚拟衬底材料.结果显示,位错被限制在LT-Si缓冲层中,弛豫度达到了85.09%,且在Si0.8Ge0.2中未观察到穿透位错,实验结果证实了赝晶Si0.8Ge0.2是通过在LT-Si缓冲层形成位错来释放应变的弛豫机理.

In the light of energy balance and screw dislocation formation model,a detailed analysis is presented on strain relaxation mechanism of pseudomorphic SiGe based on the experimental result that shear modulus of low-temperature Si （LT-Si） is less than that of SiGe. The mechanism shows that strain is relaxed by dislocation formed in LT-Si buffer layer when the thickness of pseudomorphic SiGe film is smaller than the critical thickness,and dislocations prefecentially form in LT-Si layer then the thickness of the film is equal or exceeds the critical thickness,which agrees with the experimental results reported in the literature. At the same time,an experiment was carried out to grow relaxed Si0. 8 Ge0. 2 virtual substrate using LT-Si technology. The results indicated that dislocations were resmicted to the LT-Si layer and the relaxation degree was 85. 09% without threading dislocations in Si0. 8 Ge0. 2 . The experimental results proved that the strain of pseudomorphic Si0. 8 Ge0. 2 is relaxed by dislocations formed in the LT-Si buffer layer.