Independent manipulation of density and size of stress-driven self-assembled quantum dots

Abstract

A method to independently manipulate the density and size of stress-driven self-assembled quantum dots (QDs) is demonstrated in the InAs/GaAs material system. In bilayer stacks, different InAs deposition amounts in the initial (seed) and second layer are shown to enable independent control, respectively, of the density and the size distribution of the second layer QDs. The approach allows enhancing the average volume and improving the uniformity of InAs QDs, resulting in, respectively, low and room temperature photoluminescence at 1.028 eV (∼1.2 μm) and 0.955 eV (∼1.3 μm) with remarkably narrow linewidths of 25 and 29 meV for 1.74 ML (seed)/3.00 ML InAs stacking.

Electronic Coupling in Nanoscale InAs/GaAs Quantum Dot Pairs Separated by a Thin Ga(Al)As Spacer

“…Generally, the fabrication of quantum coupled InAs/GaAs QD pair structures is implemented by growing two layers of InAs QDs with a thin GaAs spacer to form vertically aligned QD pairs. Such bilayer InAs/GaAs QD structures not only enable tuning of the quantum coupling between InAs/GaAs QDs by adjusting the GaAs spacer thickness but also provide flexibility to independently control the QD density and size as well as to improve QD uniformity [16][17][18][19]. These advantages make the vertically aligned InAs/GaAs QD pair structure an interesting choice for achieving artificial QD molecules.…”

Persistent template effect in InAs/GaAs quantum dot bilayers

“…There has been much interest in the growth of closely stacked quantum dot ͑QD͒ layers, for example, to optimize the design of device structures to maximize optical gain, 1,2 to extend their emission wavelength, 3,4 and also to develop novel applications, such as potential qubits for quantum information processing. 5,6 When there is a sufficiently small separation between two QD layers, strain from the underlying layer influences the growth conditions of an upper layer, leading to preferential nucleation of QDs above buried QDs.…”

“…7 This provides an additional control mechanism over the growth process and allows greater freedom of choice of QD properties in stacked QD layers than is possible for single layers. Typical growth parameters such as coverage, 3 temperature, 4 and growth rate 8 can be varied to tune the size and composition of QDs in the upper layer while keeping the QD density constant, since the lower ͑seed͒ layer acts as a template for QD nucleation. These InAs/GaAs QD bilayers have been successfully incorporated into edge-emitting laser structures with room temperature operation at wavelengths up to 1430 nm.…”

Optical Properties of III–V Quantum Dots

“…For a comprehensive presentation five samples with different QD structures have been examined. Samples A to C contain QDs of pure InAs, prepared employing punctuated island growth and a low temperature GaAs cap prepared using migration enhanced epitaxy to preserve a pyramidal shape [23,24]. Sample A consists of a single QD layer, samples B and C contain small InAs seed QDs and either a single active layer of InAs QDs, separated by a 36 ML thick GaAs spacer from the seed QDs, or a five-fold stack of InAs QDs with 45 ML thick GaAs spacers between all layers.…”