Regimes of GaAs quantum dot self-assembly by droplet epitaxy

Abstract

Two regimes are observed for the density of strain-free GaAs quantum dots ͑QDs͒ grown by Ga droplet epitaxy. QDs grown from liquid Ga droplets deposited at temperatures up to 200°C exhibit densities that qualitatively agree with classical nucleation theory and are quantitatively reproduced by a rate equations based growth model under consideration of dimer break off. In contrast, at higher growth temperatures, the onset of coarsening by Ostwald ripening ͓Z. Phys. Chem., Stoechiom. Verwandtschaftsl. 34, 495 ͑1900͔͒ causes drastically reduced QD densities. Extension of the growth models and consideration of Ostwald ripening allow the quantitative prediction of QD densities in this regime, as well.

Shape control of quantum dots studied by cross-sectional scanning tunneling microscopy

“…Whether intermixing of Al is a factor of importance in the formation of GaAs/AlGaAs QDs grown by droplet epitaxy is a question frequently raised in the literature [19][20][21]. In all QDs imaged we have observed some degree of intermixing.…”

Evolution of interfacial curvatures of a bicontinuous structure generated via nonconserved dynamics

“…Coarsening is a ubiquitous natural phenomenon that occurs in a wide range of materials, such as metallic alloys [1][2][3][4][5][6][7][8], polymers [9][10][11][12][13][14][15], and semiconductors [16][17][18][19][20][21]. During coarsening, the total interfacial area of a microstructure decreases to reduce excess free energy associated with the existence of phase boundaries.…”

Holed nanostructures formed by aluminum droplets on a GaAs substrate

“…A significant advantage of droplet epitaxy growth is its flexibility in that it is applicable to both latticemismatched and lattice-matched systems. Since the initial work by Koguchi et al [10], various dot-like [11][12][13], ring-like [14][15][16][17], and hole-like nanostructures [18][19][20] have been observed on Ⅲ-Ⅴ semiconductors.…”

“…The holed nanostructures, first demonstrated by Wang et al [21], are particularly promising candidates for the formation of uniform and low-density quantum rings [22][23][24]. However, all the previously published work has involved the formation of nanostructures from gallium (Ga) or indium (In) droplets [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24], and there has been no report of aluminum (Al) droplets on GaAs substrates, although there have been a few of papers involving Al droplets [11,25]. Investigation of the nanostructures formed from Al droplets will not only enrich our knowledge of group Ⅲ droplet epitaxy and facilitate an understanding of provide a solid understanding of such a simple and novel molecular beam epitaxy (MBE) growth process [26].…”