本文利用X射线双晶衍射方法,研究了分子束外延(MBE)GaAs/CaP(001)异质外延层的结构参数——晶格常数、晶胞体积.根据X射线衍射动力学理论和运动学理论分别对双晶衍射摇摆曲线的峰角位置进行了修正,二者吻合很好.修正后的结果表明:X射线双晶衍射测量中会引入一定的晶胞体积缩小量,修正后外延层的晶胞体积略大于自由状态GaAs单晶的晶胞体积,这里根据Poisson关系对 GaAs/GaP外延层晶胞体积的增大进行了解释. In this paper, the structural parameters of the GaAs / CaP (001) heteroepitaxial layer (MBE) lattice constants and unit cell volume have been studied by X-ray double crystal diffraction method. According to the X-ray diffraction kinetic theory and kinematics Theory were respectively used to correct the peak-angle position of the twin-crystal diffraction rocking curve, which is in good agreement with each other.The corrected results show that a certain amount of unit cell shrinkage will be introduced in the X-ray double crystal diffraction measurement, The unit cell volume is slightly larger than that of the free-state GaAs single crystal. Here, the increase of the unit cell volume of the GaAs / GaP epitaxial layer is explained by Poisson’s relation.