Molecular beam epitaxial growth of GaSb quantum Dots on (001) GaAs substrate with InGaAs insertion layer (original) (raw)
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Molecular beam epitaxial growth of GaSb/GaAs quantum dots on Ge substrates
Journal of Crystal Growth, 2014
We perform structural and optical investigations of GaSb/GaAs quantum dots (QDs) grown on Ge (001) substrates by molecular beam epitaxy. Anti-phase domains (APDs) of GaAs are distributed on Ge substrate after the growth of GaAs due to the growth nature of III-V compound on group IV semiconductors having polar and non-polar behaviors. The APDs affect the QD growth as demonstrated by the growth of conventional InAs QDs on this surface. For GaSb QDs, the GaSb layer is grown on GaAs APD surface and compared with the GaSb layer on conventional (001) GaAs surface. Self-assembled QDs are formed on both surfaces but structural analysis reveals evidence of shape and size differences, which is attributed to the influence of the initial surface. Photoluminescence of GaSb/GaAs QDs grown on both Ge and GaAs substrates is studied. Emission from GaSb/GaAs QDs on Ge substrate can be detected till near room temperature (270 K).
ECTI Transactions on Computer and Information Technology (ECTI-CIT), 1970
GaSb quantum dots (QDs) have been grown by solid-source molecular beam epitaxy on a 4monolayer (ML) In x Ga 1−x As (x = 0.07, 0.15, 0.20, and 0.25) to investigate the effects of In-mole-fraction of InGaAs insertion layers on the structural and optical properties of the GaSb QDs. The density of grown GaSb QDs is approximately 1.2-2.8×10 9 cm −2 on In-GaAs insertion layers which depends on the In-molefraction. Dot shape and size change substantially when In-mole-fraction of InGaAs insertion layers is varied. The uniformity of GaSb QDs improves when the indium content increases. The change in freestanding QD morphology is likely due to the modified strain at different values of indium compositions in InGaAs insertion layers. The effects of In-molefraction of InGaAs insertion layer on optical properties of the QDs are studied by photoluminescence (PL). PL results show the blueshift of the emission when the indium content in InGaAs insertion layer increases.
Growth of GaSb quantum dots on GaAs (111)A
e-Journal of Surface Science and Nanotechnology, 2014
We grew GaSb QDs on GaAs (111)A by molecular beam epitaxy (MBE). By atomic force microscopic studies, it was found that large GaSb islands with low density are formed when grown at a relatively high temperature (Ts ∼ 470 • C), suggesting the large diffusion length of Ga atoms on the substrate surface. In contrast, GaSb QDs formed at a lower temperature (Ts ∼ 430 • C) are much smaller (∼ 39 nm) in diameter and their density is much higher (∼ 5.0×10 10 cm −2), originated from the suppression of the Ga diffusion on the substrate surface. We also grew GaSb QDs at various substrate temperatures Ts and examined how Ts affects the QD radius and height.
Morphology of self-assembled InSb/GaAs quantum dots on Ge substrate
Journal of Crystal Growth, 2017
In this work, we report on the growth of self-assembled InSb/GaAs quantum dots (QDs) on (001) Ge substrate by molecular beam epitaxy. Due to the polar/non-polar nature of GaAs grown on Ge, antiphase domains are formed. Effects of the domain and QD growth temperature on the morphology of realized QDs are presented. InSb QDs are mostly formed at the antiphase-domain boundaries (APBs). The QD size, shape and density are varied with the QD growth temperature. These free-standing QDs have irregular lens and stripe-shapes with {10n} side facets according to the analysis of atomic force microscopy images. InSb QDs is formed at the APBs, where two orthogonal GaAs surfaces are met. 2. Experimental details Strain induced self-assembled InSb QDs are grown on p-type (001) Ge substrate by solid-source MBE machine (RIBER, Compact 21TM) with antimony (Sb) valved cracker cell. The Ge substrate is annealed at 500°C in As 4 rich atmosphere for surface oxide removal. The first 300 nm-thick GaAs layer is initially grown in slow Ga growth rate (0 .1 ML/s), and followed by 100 nm GaAs layer in fast Ga growth rate (~0.17 ML/s) at substrate temperature 400°C. The As 4 flux back
MRS Advances, 2016
ABSTRACTThe effects of GaAs anti-phase domains (APDs) on the growth of GaSb quantum dots (QDs) are investigated by molecular beam epitaxial growth of GaAs on Ge (001) substrate. Ge is a group-IV element and GaAs is a polar III-V compound semiconductor. Due to polar/non polar interface, GaAs APDs are formed. Initial formation of APD relates to a non-uniform growth of high index GaAs surfaces. However, due to high sticking coefficient of Sb atoms at low substrate growth temperature, GaSb QDs can be formed on the whole surface of the sample without any effects from APD boundary. The buffer layer growth temperature is one of the key roles to control the APDs formation. Therefore we tried to adjust the optimum conditions such as buffer layer thickness and growth temperature to get nearly flat sample surface with large APDs for high QDs density (∼ 8×109dots/cm2). Low-temperature photoluminescence is conducted and GaSb QDs peak is observed at the energy range of 1.0 eV-1.3 eV.
Thin GaSb insertions and quantum dot formation in GaAs by MOCVD
Journal of Crystal Growth, 2000
Self-organized formation of GaSb quantum dots during MOCVD growth has been studied. Thin GaSb layers are deposited on GaAs (0 0 1), followed by a growth interruption before the deposition of a GaAs layer. The GaSb growth is performed using low V/III ratios and growth temperatures between 5103C and 5503C. Undercritical GaSb depositions lead to inhomogenities in the composition and thickness of such layers. Photoluminescence measurements suggest these quantum islands to provide zero-dimensional con"nement for holes. The dependence of the luminescence on the growth temperatures indicates the formation of the quantum islands to be kinetically controlled.
Linking structural and electronic properties of high-purity self-assembled GaSb/GaAs quantum dots
Physical Review B, 2012
We present structural, electrical, and theoretical investigations of self-assembled type-II GaSb/GaAs quantum dots (QDs) grown by molecular beam epitaxy. Using cross-sectional scanning tunneling microscopy (X-STM) the morphology of the QDs is determined. The QDs are of high purity (∼100% GaSb content) and have most likely the shape of a truncated pyramid. The average heights of the QDs are 4-6 nm with average base lengths between 9 and 14 nm. Samples with a QD layer embedded into a pn-diode structure are studied with deep-level transient spectroscopy (DLTS), yielding a hole localization energy in the QDs of 609 meV. Based on the X-STM results the electronic structure of the QDs is calculated using 8-band k•p theory. The theoretical localization energies are found to be in good agreement with the DLTS results. Our results also allow us to estimate how variations in size and shape of the dots influence the hole localization energy.
GaSb Dots Grown on GaAs Surface by Metalorganic Chemical Vapour Deposition
Acta Physica Polonica A
We report metaloorganic chemical vapour deposition growth of an anisotropic GaSb islands on GaAs (001) surface with a typical dimensions around 200 nm. Results of investigations employing scanning electron microscope, scanning tunnelling microscope and ph9tocapacitance are presented.
Journal of Crystal Growth, 2019
The effects of growth temperature, growth rate and local growth position on the morphology of self-assembled InSb/GaAs quantum dots (QDs) on (001) Ge substrate are investigated. It is found that for low growth rates, anti-phase domain (APD) boundaries formed during the growth of GaAs on Ge can effectively act as the preferential nucleation position of InSb QDs. For high growth rates, InSb/GaAs QDs nucleate on both the APD boundary and the APD surface, leading to high density-InSb QDs. The QD morphologies on the APD boundary and the APD surface are distinctly different. The roles of growth rate and local growth position on the morphology of realized QDs are described. By varying the growth conditions, low density and locally aligned QDs as well as high density InSb QDs can be obtained.
Structural characterization of GaSb-capped InAs/GaAs quantum dots with a GaAs intermediate layer
Materials Letters, 2011
GaSb incorporation to InAs/GaAs quantum dots is considered for improving the opto-electronic properties of the systems. In order to optimize these properties, the introduction of an intermediate GaAs layer is considered a good approach. In this work, we study the effect of the introduction of a GaAs intermediate layer between InAs quantum dots and a GaSb capping layer on structural and crystalline quality of these heterostructures. As the thickness of the GaAs intermediate layer increases, a reduction of defect density has been observed as well as changes of quantum dots sizes. This approach suggests a promising method to improve the incorporation of Sb to InAs heterostructures.