Effect of the ultra-low arsenic flux on characteristics of In(As) nanostructures formed during droplet epitaxy

In this paper, we present the results of an experimental study of the influence of the ultra-low arsenic flux on the parameters of In nanodroplets obtained by droplet epitaxy on the GaAs substrate. We demonstrate that the arsenic flux can be used to alter the size of droplets without changing their surface density. An increase in the arsenic flux leads to a reduction of the nanostructure size or their complete decay. However, we demonstrate that certain growth conditions allow providing saturation of the size of nanostructures (∼30 nm) which ensures good reproducibility of the process. The mechanism of ring and hole formation at various arsenic fluxes is also discussed.

The influence of temperature and arsenic molecular form at crystallization stage on the InAs nanostructure growth during droplet epitaxy

In this work, experimental studies of the influence of the arsenic molecular form (di-or tetramers) and substrate temperature on the crystallization of In/GaAs droplet nanostructures during droplet epitaxy have been carried out. We have shown the critical influence of the temperature and arsenic molecular form on the reproducibility of the characteristics of an array of self-organizing InAs nanostructures during crystallization. We also showed that a decrease in the initial In droplet size has a positive effect on the reproducibility of the parameters of the InAs nanostructures arrays. Our work also showed important role of substrate temperature at the crystallization stage.

Study of In/GaAs nanodroplet formation in conditions of non-stationary supersaturation during droplet epitaxy

In this paper, we present the results of kinetic Monte Carlo study of the In/GaAs growth by droplet epitaxy in conditions of non-stationary vapor supersaturation. These conditions allow achievement of the independent control of size and surface density of nanostructures. The material redistribution is realized on the surface when indium deposition is interrupted and leads to a decrease in the critical thickness of droplet formation. An average droplet size increases with increase in interruption time whereas the surface density decreases. However, additional nucleation within the wetting layer can also be observed during the growth interruptions, which makes it possible to increase the surface density of droplets.

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

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 (TEM) investigations reveal buried quantum dots with truncated pyramid shape without defects or dislocations.

Enable a Facile Size Re-distribution of MBE-Grown Ga-Droplets via In Situ Pulsed Laser Shooting

A MBE-prepared Gallium (Ga)-droplet surface on GaAs (001) substrate is in situ irradiated by a single shot of UV pulsed laser. It demonstrates that laser shooting can facilely re-adjust the size of Ga-droplet and a special Ga-droplet of extremely broad size-distribution with width from 16 to 230 nm and height from 1 to 42 nm are successfully obtained. Due to the energetic inhomogeneity across the laser spot, the modification of droplet as a function of irradiation intensity (IRIT) can be straightly investigated on one sample and the correlated mechanisms are clarified. Systematically, the laser resizing can be perceived as: for low irradiation level, laser heating only expands droplets to make mergences among them, so in this stage, the droplet size distribution is solely shifted to the large side; for high irradiation level, laser irradiation not only causes thermal expansion but also thermal evaporation of Ga atom which makes the size-shift move to both sides. All of these size-shifts on Ga-droplets can be strongly controlled by applying different laser IRIT that enables a more designable droplet epitaxy in the future.