Height control of self-assembled quantum dots by strain engineering during capping

Abstract

Strain engineering during the capping of III-V quantum dots has been explored as a means to control the height of strained self-assembled quantum dots. Results of Kinetic Monte Carlo simulations are confronted with cross-sectional Scanning Tunnel Microscopy (STM) measurements performed on InAs quantum dots grown by molecular beam epitaxy. We studied InAs quantum dots that are capped by InxGa(1−x)As layers of different indium compositions. Both from our realistic 3D kinetic Monte Carlo simulations and the X-STM measurements on real samples, a trend in the height of the capped quantum dot is found as a function of the lattice mismatch between the quantum dot material and the capping layer. Results obtained on additional material combinations show a generic role of the elastic energy in the control of the quantum dot morphology by strain engineering during capping.

Investigation of the InAs/GaAs Quantum Dots’ Size: Dependence on the Strain Reducing Layer’s Position

“…This shows that the values are over estimated. Indeed, the QDs height can be reduced by the capping process [ 29 , 30 ]. Additionally, the AFM technique may also provide an over estimated size due to the tip artifact [ 31 , 32 ].…”

Tuning the properties of InAs/GaAs quantum dots through a modified capping layer: Application to optoelectronic devices

“…2.7. In good agreement with the model proposed by Grossi et al [117], the QD height was found to follow a linear tendency with the Sb content, i.e., with the lattice parameter increase of the capping material.…”

“…Contrarily an increase of the capping rate will kinetically restrain surface intermixing, facilitating the preservation of metastable QD structures and significantly increasing the aspect ratio. Remarkably, this is achieved even in a system with a high lattice mismatch between InAs QDs and GaAs CL (Δa~7%) without the use of strain-engineering strategies [117]. As observed in Fig.…”

“…U l lo a e t a l . [109,113,[115][116][117]. On the other hand, this approach additionally allows tailoring the electronic structure of the QDs and the emission wavelengths of InAs QDs have been extended to the 1.3-1.55 µm region using InGaAs [40,[118][119][120] and GaAsSb [41,42,106,121] strainreducing CLs.…”

“…Indeed, geometry and composition determine the properties of QDs [61,62], strongly affecting the performance of lasers, solar cells or any other optoelectronic devices based on QDs. Strain engineering by the use of alternative capping materials has been a commonly employed strategy in order to prevent QDs from dissolution during overgrowth offering a certain degree of control over the QD size and shape [42,110,114,[116][117][118]121,[125][126][127][128]183,184]. This occurs, however, at the expense of significant and inevitable additional electronic or structural modifications which might not be desirable in some cases.…”