Incorporation of random alloy GaBi${}_x$As${}_{1-x}$ barriers in InAs quantum dot molecules (I): energy levels and confined hole states

Abstract

Self-assembled InAs quantum dots (QDs), which have long hole-spin coherence times and are amenable to optical control schemes, have long been explored as building blocks for qubit architectures. One such design consists of vertically stacking two QDs to create a quantum dot molecule (QDM) and using the spin-mixing properties of "molecule-like" coupled hole states for all-optical qubit manipulation. In this article, the first of two papers, we introduce the incorporation of dilute GaBiAs alloys in the barrier region between the two dots. GaBiAs is expected to increase the spin-mixing of the molecular states needed for qubit operations by raising the barrier valence band edge and spin-orbit splitting. Using an atomistic tight-binding model, we compute the properties of GaBiAs and the modification of hole states that arise when the alloy is used in the barrier of an InAs QDM. An atomistic treatment is necessary to correctly capture non-traditional alloy effects such as the band-anticrossing valence band. It also allows for the study of configurational variances and clustering effects of the alloy. We find that in InAs QDMs with a GaBiAs interdot barrier, electron states are not strongly affected by the inclusion of Bi. However, hole states are much more sensitive to the presence and configuration of Bi in the barriers. By independently studying the alloy-induced strain and electronic scattering off Bi and As orbitals, we conclude that an initial increase in QDM hole state energy at low Bi concentration is caused by the alloy-induced strain. We further find that the decrease in QDM hole energy at higher Bi concentrations can only be explained when both alloy strain and orbital effects are considered. In our second article, we use the understanding developed here to discuss how the alloyed barriers contribute to enhancement in hole spin-mixing and the implications for QDM qubit architectures.

RevTex4-1, 13 pages, 17 figures

References in corpus (9)

• Quantum Computing
• Direct Observation of Controlled Coupling in an Individual Quantum Dot Molecule
• Hole - Nuclear Spin Interaction in Quantum Dots
• Electrically tunable g-factors in quantum dot molecular spin states
• Impact of alloy disorder on the band structure of compressively strained GaBiAs
• Scalable qubit architecture based on holes in quantum dot molecules
• Localization of electronic states in III-V semiconductor alloys: a comparative study
• Symmetry induced hole-spin mixing in quantum dot molecules
• Valence band splitting in bulk dilute bismides

Cited by in corpus (3)

• The magneto-optics in quantum wires comprised of vertically stacked quantum dots: A calling for the magnetoplasmon qubits
• Single-particle and collective excitations in quantum wires comprised of vertically stacked quantum dots: Finite magnetic field
• Incorporation of random alloy GaBi${}_x$As${}_{1-x}$ barriers in InAs quantum dot molecules: alloy strain and orbital effects towards enhanced tunneling