Electronic and optical properties of [110]-tilted InAs/GaAs quantum dot stacks

Abstract

Multi-million atom simulations are performed to study stacking-angle (θ) dependent strain profiles, electronic structure, and polarization-resolved optical modes from [110]-tilted quantum dot stacks (QDSs). Our calculations reveal highly asymmetrical biaxial strain distributions for the tilted QDSs that strongly influence the confinements of hole wave functions and thereby control the polarization response. The calculated values of degree of polarizations, in good agreement with the available experimental data, predict a unique property of the tilted QDSs that the isotropic polarization response can be realized from both [110] and [-110] cleaved-edges − a feature inaccessible from the conventional [001]-QDSs. Detailed investigations of polar plots further establish that tilting the QDSs provides an additional knob to fine tune their polarization properties. for the same number of QDLs in both stacks. Furthermore, a large rotation of PL polar plot peak was measured from the [-110] cleaved-edge surface leading to a discrepancy with the angle of tilt of the QDS. This appealed for a detailed understanding of the stacking-angle dependent electronic and optical properties to appropriately explain the experimental measurements. This work presents a first theoretical study of the tilted InAs QDSs by performing atomistic simulations of strain, electronic structure, and polarization-dependent inter-band optical transition strengths. The unique characteristics of the tilted QDSs are reported by highlighting highly asymmetrical biaxial strain distributions that regulate the electronic structure and polarization properties. It is predicted that by tilting the QDS, isotropic polarization response could be simultaneously realized from both [110] and [-110] cleaved- edge surfaces − a feature not accessible from the conventional [001]-aligned stacks [5][6][7] . The comparison of polar plots further revealed a high degree of control over the polarization properties attainable by tilting the QDSs, making it a useful tool for engineering the optical properties from the QD nano-structures.

Understanding the electric field control of the electronic and optical properties of strongly-coupled multi-layered quantum dot molecules

“…Self-assembled quantum dot molecules (QDMs) made up of III-V materials are one of the most popular types of nanostructures used in a variety of devices for optoelectronic [1][2][3][4][5][6][7], photovoltaic [8][9][10][11][12], and quantum information technologies [13,14]. The QDMs typically grow in the form of vertical stacks due to the presence of strain, which stems from the lattice mismatch of the substrate and the QD material.…”

“…Just as the quantum dots (QDs) are widely known as "artificial atoms" due to their discrete energy spectra and the three-dimensional confinement of the charge carriers, the strongly-coupled quantum dots are often referred as "artificial molecules" due to their hybridized bonding and anti-bonding type electronic states, closely resembling to that of the molecules made up of atoms. Self-assembled quantum dot molecules (QDMs) made up of III-V materials are one of the most popular types of nanostructures used in a variety of devices for optoelectronic [1][2][3][4][5][6][7], photovoltaic [8][9][10][11][12], and quantum information technologies [13,14]. The QDMs typically grow in the form of vertical stacks due to the presence of strain, which stems from the lattice mismatch of the substrate and the QD material.…”