Influence of growth conditions on the photoluminescence of self-assembled InAs/GaAs quantum dots

Abstract

We have investigated the influence of various growth parameters on the optical properties of self-assembled InAs/GaAs quantum dots (QDs) grown by molecular beam epitaxy (MBE) in Stranski–Krastanov mode. Metastably sized QDs have been observed in photoluminescence measurements, which are fabricated by depositing 2.5 monolayers (ML) InAs at a substrate temperature of 530 °C and As4 pressure of (1.6±0.2)×10−5 mbar. These self-assembled QDs exhibit both good optical quality and a narrow size distribution with a full width at half maximum of ∼35 meV both at room temperature and at 4.2 K. By investigating the dependence of the optical properties on the substrate temperature and arsenic pressure, we show that the diffusion length of the adatoms is responsible for changes in size, density, and quantum efficiency of the QDs beside the amount of InAs deposited. The growth conditions for fabricating QDs are optimized for substrate temperatures Ts=480 and 530 °C. A high QD density (∼1×1011 cm−2) with a broad size distribution and a lower QD density (∼1.2×1010 cm−2) with a narrow size distribution, which are determined by atomic force microscopy have been obtained by MBE growth at Ts=480 and 530 °C, respectively. Stacking several QD layers separated by thin GaAs spacers in order to achieve a higher QD density improves the optical properties of the islands. The thermal stability of the QDs has been tested by annealing the samples at high temperatures in order to determine the highest possible substrate temperature for the following expitaxial layers. The QDs grown at 530 °C can be overgrown at 700–720 °C, while the QDs grown at 480 °C can only be overgrown at 600–620 °C without obvious decrease of the quantum efficiency of the QDs.

Intraband transitions in quantum dot–superlattice heterostructures

“…Furthermore the spectral response of such devices can be controlled through the applied bias allowing multiwavelength detection 23 . It was also shown, that the electronic states within the QD can be tuned by changing the InAs dot size 10 by incorporating an AlAs layer close to the QDs 11 , or by confining the QDs in an Al x Ga 1−x As Matrix 12,24 , which causes a higher conduction band offset to InAs.…”

“…InAs quantum dots (QDs) embedded in GaAs quantum well structures have initiated considerable research activities in the recent years 1,2,3,4,5,6,7,8,9,10,11,12,13,14 . The interest in QDs is mainly based on the favorable energy spacing of their bound electronic states and the great potential to adjust these properties.…”

Growth-temperature dependence of optical spin-injection dynamics in self-assembled InGaAs quantum dots

“…With this in mind, the growth-temperature dependence of the spin-injection dynamics in QDs was systematically studied, as the growth temperature of InAs and InGaAs QDs is known to significantly affect their size, shape, density, compositional distribution and resultant strain, and also optical quality. [15][16][17] The transient behavior of the circular polarization property of photoluminescence (PL) in InGaAs QDs after optical spin generation in GaAs barriers, which directly reflects the spin-injection dynamics, is herein discussed in relation to growth temperature through the development of rate equations that incorporate all aspects of spin-injection dynamics for spin-polarized states in QDs, and their subsequent spin relaxation. These results are also compared with the dot structure, with a view to determining the optimal growth conditions for spin-functional applications.…”

Quantum Dot Superluminescent Diodes for Optical Coherence Tomography: Device Engineering

“…As the growth temperature is reduced, the indium surface migration length is reduced, acting to reduce the dot size and increase the dot density [19] through a mechanism, which favors accumulation at increasingly localized sites. These structural changes induce a blue shift in the emission energy [20], but this may be partially offset by an increase in indium incorporation at the growth front at the lower growth temperature.…”