Real time analysis of self-assembled InAs/GaAs quantum dot growth by probing reflection high-energy electron diffraction chevron image

Abstract

Self-assembling process of InAs/GaAs quantum dots has been investigated by analyzing reflection high-energy electron diffraction chevron images reflecting the crystal facet structure surrounding the island. The chevron image shows dramatic changes during the island formation. From the temporal evolution of the chevron tail structure, the self-assembling process has been found to consist of four steps. The initial islands do not show distinct facet structures. Then, the island surface is covered by high-index facets, and this is followed by the formation of stable low-index facets. Finally, the flow of In atoms from the islands occurs, which contributes to flatten the wetting layer. Furthermore, we have investigated the island shape evolution during the GaAs capping layer growth by using the same real-time analysis technique.

Influence of In and As fluxes on growth of self-assembled InAs quantum dots on GaAs(0 0 1)

“…Earlier work has documented that 2D InAs islands are formed on top of the wetting layer (WL) between 1.0 and 1.5 ML of InAs, and with further deposition 3D nuclei are formed on top, which most likely turn into QDs [6,7]. Real-time monitoring during growth were performed by reflection high-energy electron diffraction (RHEED) [13,16] or X-ray diffraction (XRD) [17] to observe the evolution directly. In our previous work, we observed by RHEED that under low growth rates of o0.02 ML/s, there are two steps in the QD formation that are flux dependent and independent, which we attributed to the flux driven nucleation and incorporation of 2D islands into the nuclei, respectively.…”

Self-assembly of InAs quantum dots on GaAs(001) by molecular beam epitaxy

“…In discussing their experimental results, Leonard et al [13] suggested that the stability of the InAs QDs against further growth is associated with a very high energy barrier for the formation of misfit dislocations in the interface area underlying an InAs QD. Alternatively, Kudo et al [292] supposed that the stability of a mature QD results from its stable faceted sidewalls, which do not incorporate additional atoms after formation.…”

“…In MBE InAs/GaAs(001), the dynamic evolution of an ensemble of QDs was generally monitored in situ via either RHEED [247][248][249][250][251], the photoluminescence optical properties [252], or XRD [253]. From these experimental observations, a timescale of at least a few seconds for InAs QD growth was extracted; this was regarded as quite fast in comparison with the deposition rate (which is usually 0.1 ML/s).…”

“…In Section 3.6, it was mentioned that the timescale for QD growth completion was estimated by techniques such as RHEED [247][248][249][250][251], photoluminescence [252], and XRD [253]. A more direct and accurate measurement method for extracting the timescale is based on snapshots obtained in neighboring regions on the growth surface using STM and ATM.…”

Annealing effects on faceting of InAs∕GaAs(001) quantum dots

“…Indeed, in comparison to experimental data in the literature ͕136͖ facets are measured when InAs growth rate is higher than 0.1 ML/ s, 22,23 while ͕137͖ facets are found when growth rate is ϳ0.01 ML/ s or less. 7,17,18 The absence of QDs with AR= 0.3 when annealing was applied is thus related to the kinetics of growth: When the system has time enough to evolve, the thermodynamically more stable ͕137͖ facet is found.…”