Study on the asymmetry of nanopore in Al droplet etching

In the local droplet etching (LDE) method, the fine split structure (FSS) of quantum dots (QDs) is directly related to the shape of the nanopores formed after annealing. The formation of highly symmetrical nanoporous is the key to the preparation of GaAs/AlGaAs QDs with small FSS. The measurement and characterization of the nano pore shape before and after annealing showed that the density of the nano pore contours is different in different directions, indicating that the slope of the sidewall of the nano pore is different. Therefore, the QDs formed by LDE still have FSS. It has also been observed in experiments that one of the reasons for the asymmetry of the nanoporous is that the etching points covered by the Al droplets on the AlGaAs surface are not in the center of the droplets, which is caused by the supersaturation and maturation of Al atoms during the formation of the droplets. The asymmetry of the annular wall of the nano pore will cause the increase of the FSS of the QDs in the shallow nano pore. When the nano pore is deep enough, the influence of the annular wall of the nano pore on the QDs can be completely ignored, which greatly simplifies the preparation of nano pore. It has certain guiding significance of the preparation of nanoporous required for the growth of QDs with small FSS.