Thermodynamic modelling of InAs/InP(0 0 1) growth towards quantum dots formation by metalorganic vapor phase epitaxy

Abstract

Quantum Dots (QDs) are considered as an efficient building block of many optoelectronic applications, such as semiconductor laser, photodetector, whereby their physical dimension is the key parameter to be controlled. In this work, we have studied experimentally the growth of InAs QDs on InP(0 0 1) substrate by MOVPE and established a theoretical model explaining the observed epitaxial behaviour. In variance with the classical Stranski-Krastanov growth, we show that during the growth there is an intermediate stage whereby although first large 3D islands are formed, an increased density of small QDs is formed concurrent with the shrinkage of the large 3D islands. As a result, the growth can be divided into three regimes: 2D layer growth, large 3D islands growth and QDs growth. To explain this evolution, a thermodynamic model has been developed accounting for the process driven by surface energy, elastic relaxation energy and inter-island interaction energy. It will be shown that the balance between the surface energy and the elastic relaxation energy provides the transition from 2D layer to large 3D islands (around at 3 ML of InAs growth). This model also supports the energetically favourable truncated pyramidal shape for large 3D islands and the spherical cap shape for QDs. We show in this paper that a balance between surface energy, elastic relaxation energy and inter-island elastic interaction explains the volume shrinkage of the early large 3D islands towards the formation of small QDs in high density.

Control of Morphology and Substrate Etching in InAs/InP Droplet Epitaxy Quantum Dots for Single and Entangled Photon Emitters

“…On the other hand, QDs in layer A2 (Figure c,d) are perfectly trapezium-shaped (truncated pyramids in 3D) with a flat and long top facet and reduced height compared to QDs in layer A1. This is due to the fact that QDs in layer A2 were capped at higher temperature (520 °C), and it is well-known that the high-temperature capping induces the leveling of QDs due to the increased mass transfer from the QD apex to the sides. − Two distinct features can be observed in Figure : (1) a small etch pit of nearly pure InAs is visible underneath the QD in Figure a; (2) the QDs in layer A2 (Figure c,d) appeared to be elevated compared to the wetting layer due to the formation of trenches around the QDs. The two features are a direct result of the change in the substrate etching mechanism due to the increased crystallization temperature from layer A1 (480 °C) to layer A2 (520 °C) and are explained in detail in section .…”

Tailoring of AlAs/InAs/GaAs QDs Nanostructures via Capping Growth Rate

“…Figure 3 c is a plot of the average QD volume as a function of the CGR making a distinction on the QD shape. In general, the truncated pyramid shape was more common for larger QDs, while the lens shape was preferable for smaller QD volumes [ 35 ]. As can be seen, the few truncated pyramid-shaped QDs were twice as large as the lenticular ones for the lowest CGR.…”

Fine-tunable near-critical Stranski-Krastanov growth of InAs/InP quantum dots

“…The systematic investigation of this regime for InAs QDs formation on GaAs substrates is difficult due to a rather small critical thickness h c ≈ 1.7 ML, which is close to h eq [25]. In contrast, InAs/InP system has a larger difference between h c of around 4 ML and h eq of around 3 MLs according to recent experimental observations [10].…”