沉积温度对GaAs薄膜微观结构的影响

Influences of depositing temperature on the microstructure of GaAs film

为探讨沉积温度对GaAs薄膜外廷生长过程中微观结构的影响，运用分子动力学方法模拟不同沉积温度时的GaAs薄膜外延生长过程．结果表明：在温度低于800K时，沉积薄膜的晶格完整度和临界外延生长厚度随沉积温度的升高而增加；当沉积温度在800～1500K时，晶格完整度随沉积温度的升高变化较为平缓，但此时薄膜中仍含有一定的点缺陷．随着温度的升高，点缺陷逐渐减少．As2的吸附率对温度的变化较为敏感，当沉积温度高于800K时，As2开始睨吸，致使沉积薄膜中As原子比例随沉积温度的升高而降低．在整个沉积过程中，Ga的吸附率较为稳定，在温度低于1000K时，其吸附率几乎为100％；在1000K时，Ga逐渐发生少量脱吸；在温度高于1400K时，Ga才发生明显脱吸．

Molecular dynamic simulations were used to investigate the influences of depositing temperature on the microstructure of GaAs film during molecular beam epitaxy. Results show that the lattice perfection and critical epitaxy thickness increase as the depositing temperature is increased but less than 800 K. While between 800 K and 1500 K, the lattice perfection displays less dependence on the depositing temperature, and the point defects in the film decrease with the temperature increasing. Arsenic dimer adsorption is sensitive to the growth temperature. Desorption of arsenic dimmer occurres when the depositing temperature increases above 800 K, which results in the decreasing of As fraction in the film with higher growth temperature. However, it is found that nearly 100% of gallium atomsstuck to the surface at temperature below 1000 K. Demrption of Gallium is only found when the depositing temperature increases up to 1000 K, and be enhanced when above 1400 K.