Strained Heterostructure

• Assume

  • Lattice Constant of Si substrate 为Si衬底的晶格常数
  • Lattice Constant of the SiGe bulk film 为SiGe薄片的晶格常数

• If the epitaxially grown SiGe is very thin, the heterostructure will be strained. 如果外延生长的SiGe非常薄，这个异质结就会被拉紧（应变）

• In this case, the normal cubic unit cell of the grown SiGe film , will be distorted to a tetragonal cell . That is, , and . 在这种情况下，SiGe外延薄片的正常立方晶胞（）会变为长方体晶胞（），这意味着，注意

• The strain parallel to the interface is 平行于界面的应力为

• The strain perpendicular to the interface 垂直于界面的应力为

• The substrate-film lattice mismatch (or misfit) is defined as: 衬底-薄片的错配度被定义为$$M=\frac{a_s-a_f}{a_f}$$$MM$与平行于界面的应力相同