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.
Highlights
Driven by tensile strain, GaAs quantum dots (QDs) self-assemble on In0.52Al0.48As(111)A surfaces latticematched to InP substrates
In this paper we demonstrate that an anomalous SK growth mode governs the self-assembly of GaAs tensile-strained QDs (TSQDs), wherein the wetting layer (WL) thickness is tunable
Using Atomic force microscopy (AFM), we see that for deposition
Summary
GaAs quantum dots (QDs) self-assemble on In0.52Al0.48As(111)A surfaces latticematched to InP substrates. 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. WL thickness can have significant influence on QD band structure, affecting emission wavelength[8,9,10,11], band edge profile[11], carrier confinement depth[8,9], excited state and charged exciton energy levels[8,9], QD-WL interaction strength[8], and WL interface fluctuations[12,13] These effects have important implications for QD devices[8,9,10,11,12,14,15], our ability to take advantage of them is hindered by the fact that the maximum WL thickness, tc, is a fixed parameter in conventional SK self-assembly[2,7,8,9,10,11,15]. Using a combination of microscopy, spectroscopy and computational modeling, we demonstrate that GaAs deposition beyond tc increases both QD size and WL thickness, in contrast with conventional SK growth
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