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

Abstract

Driven by tensile strain, GaAs quantum dots (QDs) self-assemble on In0.52Al0.48As(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.

Nucleation of Ga droplets self-assembly on GaAs(111)A substrates

“…These are necessary to reduce the fine structure splitting of the exciton state for the generation of highly entangled photons 9 – 11 . The QD self-assembly on (111) surfaces is complex using the Stranski-Krastanov (SK) growth mode 12 (only recently the self-assembly of SK QDs on the (111)A surface was demonstrated 13 , 14 by taking profit of tensile strain). Nevertheless, DE allows the density and the size control of the self-assembled QDs on (111)A surfaces 11 , 15 .…”

Telecom-wavelength InAs QDs with low fine structure splitting grown by droplet epitaxy on GaAs(111)A vicinal substrates

“…The common Stranski-Krastanov (SK) growth mode seen in the InAs/GaAs system [11] is not able to induce the self-assembly of QDs on (111) surfaces because of the rapid relaxation of compressive strain due to the low threshold energy for the insertion of misfit dislocations at the substrate epilayer interface [12,13]. However, by turning from compressive to tensile strain epilayers, selfassembly SK GaAs QDs on InAl(Ga)As(111)A were demonstrated [14][15][16]. A more efficient and reliable method of obtaining self-assemble QDs on (111) substrate is Droplet Epitaxy (DE)…”

Rational synthesis of atomically thin quantum structures in nanowires based on nucleation processes

“…S4.) The activation energy for band A corresponds to those of (111)-oriented InAs QDs 36 . The rate parameter for the A1 and A2 were 5.9 × 10 5 and 1.75 × 10 6 , respectively.…”