Atomic assembly during GaN film growth : Molecular dynamics simulations
Atomic assembly during GaN film growth : Molecular dynamics simulations
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DOI：
10.1103/physrevb.73.045337
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发表时间：
2006-01
影响因子：
3.7
通讯作者：
Xiaowang W. Zhou;D. Murdick;B. Gillespie;H. Wadley
中科院分区：
文献类型：
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作者：
Xiaowang W. Zhou;D. Murdick;B. Gillespie;H. Wadley
采用分子动力学模拟方法，研究了0001纤锌矿GaN薄膜的生长机理。沉积的纤锌矿晶格结构的结晶度和化学计量被确定为生长温度和N：Ga流量比的函数。当生长温度提高到500 K时，晶格完整性得到改善.在固定的生长温度下，晶格质量和化学计量都达到最佳的N：Ga比接近2和3之间的值。随着生长温度的升高，最佳通量比增大。这三个观察结果与纤锌矿相促进衬底上生长的实验研究一致。负责这些效果的原子组装机制已被探索使用时间分辨的原子位置图像。分析表明，高品质的晶体生长时，发生的非晶格原子，通常与非晶胚胎或缺陷复合物形成的沉积过程中能够移动到未占用的晶格位置通过热激活扩散过程。需要高的N：Ga通量比来合成化学计量膜，因为影响富N的0001 GaN表面的许多氮吸附原子被再蒸发。衬底温度的降低减少了这种再蒸发，因此，作为生长温度降低，减少了最佳的N：Ga比的化学计量膜的形成和最佳的晶格完整性。
Molecular dynamics simulations using a recently developed Ga-N Tersoff type bond order interatomic potential have been used to investigate the growth mechanisms of 0001 wurtzite GaN films from thermalized atomic gallium and nitrogen fluxes. The crystallinity and stoichiometry of the deposited wurtzite lattice structures were determined as a function of growth temperature and N:Ga flux ratio. The lattice perfection was found to improve as the growth temperature was increased to 500 K. At a fixed growth temperature, the lattice quality and stoichiometry both reached optimum as the N:Ga ratio approached a value between two and three. The optimum flux ratio increased with increasing growth temperature. These three observations are consistent with experimental studies of growth on wurtzite phase promoting substrates. The atomic assembly mechanisms responsible for these effects have been explored using time-resolved atom position images. The analysis revealed that high quality crystalline growth only occurred when off-lattice atoms which are usually associated with amorphous embryos or defect complexes formed during deposition were able to move to unoccupied lattice sites by thermally activated diffusion processes. The need for a high N:Ga flux ratio to synthesize stochiometric films arises because many of the nitrogen adatoms that impact N-rich 0001 GaN surfaces are re-evaporated. Reductions of the substrate temperature reduce this reevaporation and as a result, the optimum N:Ga ratio for the stoichiometric film formation and best lattice perfection was reduced as the growth temperature was decreased.