Formation of Ultra-low Density (≤10⁴cm^-2) Self-Organized InAs Quantum Dots on GaAs by a Modified Molecular Beam Epitaxy Method

Abstract

We have studied a self-assembled growth technique to form ultra-low density InAs quantum dots on GaAs by molecular beam epitaxy. After growing a GaAs layer under a particular condition, we have deposited an InAs layer of far less than the critical thickness and performed an annealing process. By optimizing these process steps, the density of dots is successfully controlled over a wide range from 10 4 to 10 8 cm À2 , at which the average interdot distance gets as long as 100 m. Photoluminescence spectra of low dot density samples have shown discrete single-dot features even under a macroscopic optical excitation. These dots are found to be formed preferentially on GaAs mounds especially when the dot density is around 2:5 Â 10 5 cm À2 . #

Bright Single-Photon Source at 1.3 μm Based on InAs Bilayer Quantum Dot in Micropillar

“…To realize InAs/GaAs QD SPSs at telecom band, their emission wavelength must extend from the usual one ~0.9 to 1.3 or 1.55 μm and their density must keep as low as 10 7 –10 8  cm −2 to realize single QDs in a microregion. To fabricate low-density InAs QDs by molecular beam epitaxy (MBE), some constructive schemes have been proposed, such as ultralow growth rate [3], high growth temperature [7–9], and precise control of deposition amount [10] of QDs and the isolation of QDs by growth on a mesa/hole-patterned substrate [11] or etching into micropillars [12, 13]. To extend their emission wavelength, several techniques have been developed, such as strain engineering of QDs [14], metamorphic structures [2], and strain-coupled bilayer QD (BQD) structure [15–17].…”

InAs/GaAs quantum dots with wide-range tunable densities by simply varying V/III ratio using metal-organic chemical vapor deposition

“…However, low-density QDs are relatively harder to acquire. Still several approaches have been developed to obtain low-density QDs structures by extremely low growth rate or precise control of the coverage close to the onset of two-dimensional (2D) to three-dimensional (3D) transition [9,10]. Additionally, some novel approaches such as modified droplet epitaxy [11,12] and pre-patterning by electron beam lithography combined with etching techniques [13,14] are also used to grow low-density QDs.…”

In situ CBrCl3 etching to control size and density of InAs/GaAs quantum dots

“…Some techniques have been reported to obtain a low density of QDs for fabrication of single QD devices [7][8][9][10][11][12][13]. Thermal annealing is one of the commonly used techniques to control the size and density of InAs dots.…”

“…Thermal annealing is one of the commonly used techniques to control the size and density of InAs dots. Ohmori et al [11] reduced the density of InAs QDs to $ 10 4 cm À 2 by a combination of molecular beam epitaxial growth of an InAs layer thinner than the critical thickness on GaAs and subsequent annealing for 1 min. Recently, Ryu et al [12] developed another technique, in which 3 monolayers (MLs) of InAs were deposited by migration enhanced epitaxy and then annealed at various temperatures so as to control the dot density (10 6 -10 10 cm À 2 ).…”