Recovery kinetics in high temperature annealed AlN heteroepitaxial films

Based on the experimental dislocation annihilation rates, vacancy core diffusion-controlled dislocation climb was found as a dominant recovery mechanism in high temperature annealing of AlN heteroepitaxial films. Dislocation annihilation mechanisms via dislocation glide (with or without kinks) and vacancy bulk diffusion were found to be less significant. Cross-slip was also ruled out as a possible mechanism as a majority of dislocations in heteroepitaxial AlN films are threading edge dislocations. While dislocation climb through both vacancy bulk and core diffusion could offer a plausible explanation of the recovery process, the activation energy for the vacancy core diffusion-controlled dislocation climb was relatively low (4.3 ± 0.1 eV), as estimated from an Arrhenius plot. The validity of the vacancy core diffusion mechanism was also supported by a large vacancy mean free path (∼240 nm), which was comparable to the sample thickness and thus the average dislocation length. Finally, the experimentally observed dislocation density reduction as a function of the annealing temperature and time was in good agreement with the vacancy core diffusion mechanism.

基于实验测得的位错湮灭速率，在氮化铝异质外延薄膜的高温退火过程中，发现空位核心扩散控制的位错攀移是主要的回复机制。通过位错滑移（有或无扭折）以及空位体扩散的位错湮灭机制被发现不太显著。由于异质外延氮化铝薄膜中的大多数位错是穿透刃型位错，所以交滑移也被排除作为一种可能的机制。虽然通过空位体扩散和核心扩散的位错攀移都可以对回复过程提供合理的解释，但从阿累尼乌斯曲线估算出空位核心扩散控制的位错攀移的激活能相对较低（4.3±0.1电子伏特）。较大的空位平均自由程（约240纳米）也支持了空位核心扩散机制的有效性，该平均自由程与样品厚度以及平均位错长度相当。最后，实验观察到的位错密度随退火温度和时间的降低与空位核心扩散机制高度吻合。