Photoluminescence from low temperature grown InAs/GaAs quantum dots

The authors investigated a set of self-assembled InAs/GaAs quantum dots (QDs) formed by mol. beam epitaxy at low temp. (LT, 250 DegC) and postgrowth annealing. A QD photoluminescence (PL) peak around 1.01 eV was obsd. The PL efficiency quickly quenches between 6 and 40 K due to the tunneling out of the QD into traps within the GaAs barrier. The PL efficiency increases by a factor of 45-280 when exciting below the GaAs band gap, directly into the InAs QD layer. This points towards good optical quality QDs, which are embedded in a LT-GaAs barrier with a high trapping efficiency. [on SciFinder (R)

Wavelength controlled multilayer-stacked linear InAs quantum dot arrays on InGaAsP/InP(100) by self-organized anisotropic strain engineering : a self-ordered quantum dot crystal

Multilayer-stacked linear InAs quantum dot (QD) arrays are created on InAs/InGaAsP superlattice templates formed by self-organized anisotropic strain engineering on InP (100) substrates in chemical beam epitaxy. Stacking of the QD arrays with identical emission wavelength in the 1.55 µm region at room temperature is achieved through the insertion of ultrathin GaAs interlayers beneath the QDs with increasing interlayer thickness in successive layers. The increment in the GaAs interlayer thickness compensates the QD size/wavelength increase during strain correlated stacking. This is the demonstration of a three-dimensionally self-ordered QD crystal with fully controlled structural and optical properties

Formation of InAs quantum dot arrays on GaAs (100) by self-organized anisotropic strain engineering of a (In,Ga)As superlattice template

We demonstrate the formation of well-defined InAs quantum dot (QD) arrays by self-organized engineering of anisotropic strain in a (In,Ga)As/GaAs superlattice (SL). Due to the accumulation and improvement of the uniformity of the strain-field modulation along [011], formation of InAs QD arrays along [0-11] with 140 nm lateral periodicity is clearly observed on the SL template when the number of SL periods is larger than ten. By enhancing the In adatom surface migration length at low growth rates, clear arrays of single InAs QDs are obtained. The QD arrays exhibit strong photoluminescence efficiency that is not reduced compared to that from InAs QD layers on GaAs. Hence, ordering by self-organized anisotropic strain engineering maintains the high structural quality of InAs QD

Effect of annealing on formation of self-assembled (In,Ga)As quantum wires on GaAs (100) by molecular beam epitaxy

The role of annealing for (In,Ga)As self-organized quantum wire (QWR) formation on GaAs (100) during growth of (In,Ga)As/GaAs superlattice (SL) structures is studied by X-ray diffraction (XRD), atomic force microscopy (AFM), and photoluminescence (PL) spectroscopy. XRD and AFM evidence that annealing after the supply of each layer of elongated (In,Ga)As quantum dots (QDs) in the SL is the crucial process for QWR formation. We conclude that during annealing, the shape anisotropy of the QDs is enhanced due to anisotropic mass transport and the QDs become connected along the [0-11] direction. Strain reduction by In desorption, revealed by XRD and PL, which accompanies this process, then results in well defined, uniform QWR arrays by repetition in SL growt

Ion channeling for strain analysis in buried nanofilms (

The title should have been: \"Ion channeling for strain anal. in buried nanofilms

Wavelength tuning of InAs/InP quantum dots: Control of As/P surface exchange reaction

Wavelength tuning of single and vertically stacked InAs quantum dot [QD] layers embedded inInGaAsP/InP [100] grown by metal organic vapor-phase epitaxy is achieved by controlling theAs/P surface exchange reaction during InAs deposition. The As/P exchange reaction is suppressedfor decreased QD growth temperature and group V-III flow ratio, reducing the QD size andphotoluminescence [PL]emission wavelength. The As/P exchange reaction and QD PL wavelengthare then reproducibly controlled by the thickness of an ultrathin [0¿2 ML] GaAs interlayerunderneath the QDs. Submonolayer GaAs coverages result in a shape transition from QDs toquantum dashes at low group V-III flow ratio. Temperature dependent PL measurements revealexcellent optical properties of the QDs up to room temperature with PL peak wavelengths in thetechnologically important 1.55 ¿region for telecom applications. Widely stacked QD layers arereproduced with identical PL emission to increase the active volume, while closely stacked QDlayers reveal a systematic PL redshift and linewidth reduction due to vertical electronic couplingwhich is proven by the linear polarization of the cleaved-side PL changing from in plane toisotropic. ¿ 2006 American Vacuum Society

Photoluminescence from low temperature grown InAs/GaAs quantum dots

The authors investigated a set of self-assembled InAs/GaAs quantum dots (QDs) formed by mol. beam epitaxy at low temp. (LT, 250 DegC) and postgrowth annealing. A QD photoluminescence (PL) peak around 1.01 eV was obsd. The PL efficiency quickly quenches between 6 and 40 K due to the tunneling out of the QD into traps within the GaAs barrier. The PL efficiency increases by a factor of 45-280 when exciting below the GaAs band gap, directly into the InAs QD layer. This points towards good optical quality QDs, which are embedded in a LT-GaAs barrier with a high trapping efficiency. [on SciFinder (R)

Role of surface morphology for InAs quantum dot or dash formation on InGaAsP/InP (100)

We investigate the formation of self-assembled InAs quantum structures on lattice-matched InGaAsP on InP (100) substrates grown by chemical beam epitaxy. The surface morphology of the InGaAsP buffer layer plays a key role for the formation of InAs quantum dots (QDs) or dashes (QDashes). QDash formation is always accompanied by a rough buffer layer surface. Growth conditions such as higher growth temperature, larger As flux, and compressive buffer layer strain promote the formation of QDs. However, once, the buffer layer has a rough morphology, QDashes always form during InAs deposition. On the other hand, well-shaped and symmetric QDs are reproducibly formed on smooth InGaAsP buffer layers for the same InAs growth conditions. Hence, not the growth conditions during InAs deposition, but rather the surface morphology of the buffer layer determines the formation of QDs or QDashes, which both exhibit high optical quality