Feddersen Stefan, Zolatanosha Viktoryia, Alshaikh Ahmed, Reuter Dirk, Heyn Christian
Center for Hybrid Nanostructures (CHyN), University of Hamburg, Luruper Chaussee 149, D-22761 Hamburg, Germany.
Department of Physics, Paderborn University, Warburger Str. 100, D-33098 Paderborn, Germany.
Nanomaterials (Basel). 2023 Jan 23;13(3):466. doi: 10.3390/nano13030466.
Site-controlled Ga droplets on AlGaAs substrates are fabricated using area-selective deposition of Ga through apertures in a mask during molecular beam epitaxy (MBE). The Ga droplets can be crystallized into GaAs quantum dots using a crystallization step under As flux. In order to model the complex process, including the masked deposition of the droplets and a reduction of their number during a thermal annealing step, a multiscale kinetic Monte Carlo (mkMC) simulation of self-assembled Ga droplet formation on AlGaAs is expanded for area-selective deposition. The simulation has only two free model parameters: the activation energy for surface diffusion and the activation energy for thermal escape of adatoms from a droplet. Simulated droplet numbers within the opening of the aperture agree quantitatively with the experimental results down to the perfect site-control, with one droplet per aperture. However, the model parameters are different compared to those of the self-assembled droplet growth. We attribute this to the presence of the mask in close proximity to the surface, which modifies the local process temperature and the As background. This approach also explains the dependence of the model parameters on the size of the aperture.
在分子束外延（MBE）过程中，通过掩膜中的孔径进行Ga的区域选择性沉积，在AlGaAs衬底上制备了位置可控的Ga液滴。利用在As通量下的结晶步骤，可将Ga液滴结晶为GaAs量子点。为了对包括液滴的掩膜沉积以及热退火步骤中液滴数量减少在内的复杂过程进行建模，对AlGaAs上自组装Ga液滴形成的多尺度动力学蒙特卡罗（mkMC）模拟进行了扩展，以用于区域选择性沉积。该模拟仅有两个自由模型参数：表面扩散的活化能和吸附原子从液滴热逃逸的活化能。在孔径开口内模拟的液滴数量与实验结果在定量上相符，直至实现完美的位置控制，即每个孔径一个液滴。然而，与自组装液滴生长的模型参数相比，这些模型参数有所不同。我们将此归因于靠近表面的掩膜的存在，它改变了局部过程温度和As背景。这种方法还解释了模型参数对孔径大小的依赖性。
