Mechanisms of ring and island formation in lattice mismatched droplet epitaxy

Abstract

Lattice mismatched GaSb nanostructures were grown using droplet epitaxy. In this method, liquid Ga droplets are deposited on GaAs substrates and then exposed to a Sb flux at various temperatures. At increasing temperature and droplet volumes, the morphologies changed from two-dimensional islands to nanoholes, three-dimensional islands, rings, and clusters of islands. A theoretical model describes the relationship between the volume of the droplet and the final nanostructure, and is validated by kinetic Monte Carlo simulations. The combined experimental and simulation results demonstrate another process to obtain complex nanostructures, widening the design window for devices. V

Precise shape engineering of epitaxial quantum dots by growth kinetics

“…A III-column element molecular beam is initially supplied for the formation of droplets on the substrate surface in vacuum, and subsequently an As flux is used for the crystallization of droplets into the III-As nanostructures. With a suitable selection of growth conditions, and by carefully controlling the group-III crystallization kinetics into a III-V semiconductor, it is possible to engineer the final shape of the nanocrystals from islands [25,[27][28][29], rings [30,31], wires [32,33], and even more complex structures [34][35][36][37][38][39].…”

Droplet destabilization during Bi catalyzed vapor-liquuid-solid growth of GaAs

“…This is in contrast to liquid Ga, which is known to etch deep holes into GaAs. 30,31 If the Bi BEP is slightly higher than the rate of desorption, the droplet size will increase very gradually during VLS growth. Figure 2 shows SEM images of the concurrent deposition of Ga, As, and Bi at 2 Â 10 À7 , 1 Â 10 À6 , and 5 Â 10 À7 Torr BEP, respectively, for 10 min.…”

GaSb/GaAs quantum-ring-with-dot structures grown by droplet epitaxy

“…In this work, the droplet size and density can be controlled by T d which governs the diffusion length of Ga atoms. Thus, the QD formation would be responsible for the strain relaxation [8]. 1.…”

“…The nanostructure shape is quite circular because of an isotropic diffusion of Ga atoms on the GaSb surface formed by the Sb-for-As exchange reaction during crystallization [7,8]. The nanostructure shape is quite circular because of an isotropic diffusion of Ga atoms on the GaSb surface formed by the Sb-for-As exchange reaction during crystallization [7,8].…”

“…Even this scenario is suitable for infrared photodetectors [2], solar cells [3], and memory applications [1], it is not good for the light-emitting devices. To fabricate the GaSb QRs on GaAs, most of techniques are dedicated to the growth of GaSb QDs by a Stranski-Krastanov (SK) mode and applying the As-for-Sb exchange reaction through post-soaking with a proper Sb/As flux ratio [2] or capping with GaAs layer [6], whereas very few studies on GaSb QRs grown by droplet epitaxy, which is a simple method, have been reported [7,8]. Besides, it has been proved that GaSb QRs have less strain and fewer defects than GaSb QDs [4], enabling the growth of multi-stacked solar cells, which can improve the efficiency [5].…”