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摘要
Dislocation-free InGaAs micro-disks, having a diameter of approximately 5 mu m and a thickness of approximately 0.2 mu m, have been grown on Si(111) substrate patterned with SiO2, with excellent uniformity in shape. This shape uniformity was dependent on the initial growth of InAs on Si windows. For the growth of well-controlled lateral islands, it is mandatory to cover the openings completely with a single-domain InAs crystal prior to the subsequent growth of InGaAs, the Ga content of which is essential for lateral growth. Moreover, the shape uniformity of InAs islands strongly affected the uniformity of the InGaAs islands' shape. On the basis of these observations, the diameter of Si openings was reduced to 1 mu m to make it easier to fill the openings with InAs without failure. A two-step growth of InAs was devised to achieve void-less nucleation and lateral growth at the same time. It was also found that the recess at the boundary between Si and the SiO2 mask played a vital role to limit the lateral size of InAs islands: when an InAs island hit that boundary, the lateral growth was suppressed and a stable {-110} facet emerged, and the growth seemed to wait for all the {-110} sidewalls to emerge. This mechanism compensated variation in the progress of InAs growth due to scattered timing of InAs nucleation. Therefore, for the purpose of improving the shape uniformity of InGaAs micro-disks, transition from InAs to InGaAs growth should be attempted after all the sidewalls are covered with {-110} facets and before vertical growth starts.
- 出版日期2012-8-1
