Anomalous Stranski-Krastanov growth of (111)-oriented quantum dots with tunable wetting layer thickness

Driven by tensile strain, GaAs quantum dots (QDs) self-assemble on In_0.52Al_0.48As(111)A surfaces lattice-matched to InP substrates. In this study, we show that the tensile-strained self-assembly process for these GaAs(111)A QDs unexpectedly deviates from the well-known Stranski-Krastanov (SK) growth mode. Traditionally, QDs formed via the SK growth mode form on top of a flat wetting layer (WL) whose thickness is fixed. The inability to tune WL thickness has inhibited researchers' attempts to fully control QD-WL interactions in these hybrid 0D-2D quantum systems. In contrast, using microscopy, spectroscopy, and computational modeling, we demonstrate that for GaAs(111)A QDs, we can continually increase WL thickness with increasing GaAs deposition, even after the tensile-strained QDs (TSQDs) have begun to form. This anomalous SK behavior enables simultaneous tuning of both TSQD size and WL thickness. No such departure from the canonical SK growth regime has been reported previously. As such, we can now modify QD-WL interactions, with future benefits that include more precise control of TSQD band structure for infrared optoelectronics and quantum optics applications.