Influence of the aspect ratio on the hole occupation. The influence of the occupation and diameter of the holes depending on the aspect ratio is given for 10 (a) and 15 s (b) of etching time. With this basic approach of two separated exposure spots, the diameter of the holes increases with decreasing aspect ratio. The advantage of a hole with smaller aspect ratio therefore comes with a disadvantage of a larger hole. Nevertheless, a smaller number of QDs per hole nucleate with decreasing aspect ratio but larger hole size. This can be seen for both etching times shown. Increasing the etching time leads to larger holes as seen before, but smaller aspect ratio and thus smaller occupation.
Mayer et al. Nanoscale Research Letters 2013 8:504 doi:10.1186/1556-276X-8-504