GaN-蓝宝石异质厚膜体系界面应力特性研究

Abstract

考虑两条假设：a) 去除Stoney模型中膜厚远小于基底厚度的近似条件，考虑GaN膜的厚度和基底蓝宝石的厚度相当。b) 把GaN的膜厚考虑成非均匀的，随面内径向坐标r变化。在此两条假设基础上研究了GaN-蓝宝石异质厚膜体系的曲率和界面剪切应力，其中将GaN的膜厚取为坐标r的正弦函数，且研究了从系统中心到边缘膜厚的薄–厚–薄和厚–薄的两种变化模式，计算结果表明系统的曲率不再是常量而是随坐标r变化的变量，界面剪切应力在整个半径R范围内出现方向的转变，转变点正好对应曲率取极值的点，可见曲率对界面剪切应力有重要影响，根本原因来源于我们考虑了GaN膜厚的非均匀性。Based on two hypothesis: a) eliminating the approximate condition that the thickness of film is far less than that of substrate adopted by Stoney model, and considering that the film thickness of GaN is comparable to that of Sapphire substrate; b) taking the GaN film as a film with non-uniform thickness which changes with r, we investigate the curvature and interface shear stress of GaN- Sapphire hetero-thick-film system. In addition, we take the film thickness of GaN as sinusoidal function of r, and study two types of film thickness variation, i.e. the thin-thick-thin model and thick-thin model. The results reveal that the system curvature is not a constant but a variable which changes with r. The interface shear stress shows a behavior of direction transition within the range of R, and transition point just corresponds to the extreme point of curvature, indicating that the curvature has a significant influence on the interface shear stress, which originates from our consideration of the non-uniform film thickness for GaN.