Droplet epitaxy of InAs/InP quantum dots via MOVPE by using an InGaAs interlayer

Abstract

InAs quantum dots (QDs) are grown on an In0.53Ga0.47As interlayer and embedded in an InP(100) matrix. They are fabricated via droplet epitaxy (DE) in a metal organic vapor phase epitaxy (MOVPE) reactor. Formation of metallic indium droplets on the In0.53Ga0.47As lattice-matched layer and their crystallization into QDs is demonstrated for the first time in MOVPE. The presence of the In0.53Ga0.47As layer prevents the formation of an unintentional non-stoichiometric 2D layer underneath and around the QDs, via suppression of the As-P exchange. The In0.53Ga0.47As layer affects the surface diffusion leading to a modified droplet crystallization process, where unexpectedly the size of the resulting QDs is found to be inversely proportional to the indium supply. Bright single dot emission is detected via micro-photoluminescence at low temperature, ranging from 1440 to 1600 nm, covering the technologically relevant telecom C-band. Transmission electron microscopy investigations reveal buried quantum dots with truncated pyramid shape without defects or dislocations.

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

“…We studied many topographic images, and we conclude that the local drilling effect is absent in all the DEQDs in sample B. From the 200 nm long image shown in Figure a, it is evident that the long-range-etching effect shown in Figure b is also suppressed, as expected from previous AFM and TEM investigations . Yoon et al suggested that this is a result of the change in the growth kinetics from the mass-transport regime on InP to the surface-reaction-limited regime on InGaAs.…”

“… 22 Here, we discuss the mechanism of such trench formation for the first time with atomic resolution. We show that both etching processes can be suppressed by growing a thin InGaAs interlayer prior to the droplet deposition as suggested by Sala et al 35 QDs crystallized at 520 °C have lower size inhomogeneity compared to QDs crystallized at 480 °C. We note that, in our previous work, 34 the indium droplets were formed at 400 °C and the crystallization temperature was up to 500 °C.…”

“…It is difficult to differentiate the quasi-WL (first 1–2 BLs) on top of the InGaAs layer, but we observe a dilute InAs(P) layer in the capping region with a similar As concentration as in layer A2 due to the segregation of As atoms in the growth direction. The insertion of the InGaAs layer prior to the indium droplet deposition significantly reduces the As–P surface exchange and modifies the surface adatom mobility compared to InP, as also pointed out by Sala et al 35 Therefore, insertion of a thin InGaAs layer is an efficient method to suppress the substrate etching and reduce the surface As–P exchange in InAs/InP DEQDs.…”

“…From the 200 nm long image shown in Figure 5 a, it is evident that the long-range-etching effect shown in Figure 4 b is also suppressed, as expected from previous AFM and TEM investigations. 35 Yoon et al 46 suggested that this is a result of the change in the growth kinetics from the mass-transport regime on InP to the surface-reaction-limited regime on InGaAs. We analyzed the QDs grown on InGaAs, crystallized at both 480 and 520 °C, and observed that both etching effects are absent.…”

“…Thus, by forming droplets on a thin InGaAs layer, we can suppress all of these effects. The surface As–P exchange strongly influences the QD morphology, and in the past, a lattice-matched InGaAs layer was used mainly to suppress the surface As–P exchange. ,,, The filled-state topographic images in Figure show the size and shape of InAs DEQDs formed on top of a 5 nm InGaAs layer. The DEQDs are truncated pyramid shaped with observable contrast fluctuations within the QD.…”