Electronic states of (InGa)(AsSb)/GaAs/GaP quantum dots

Abstract

Detailed theoretical studies of the electronic structure of (InGa)(AsSb)/GaAs/GaP quantum dots are presented. This system is unique since it exhibits concurrently direct and indirect transitions both in real and momentum space and is attractive for applications in quantum information technology, showing advantages as compared to the widely studied (In,Ga)As/GaAs dots. We proceed from the inspection of the confinement potentials for k = 0 and k = 0 conduction and k = 0 valence bands, through the formulation of k · p calculations for k-indirect transitions, up to the excitonic structure of Γ-transitions. Throughout this process we compare the results obtained for dots on both GaP and GaAs substrates, enabling us to make a direct comparison to the (In,Ga)As/GaAs quantum dot system. We also discuss the realization of quantum gates.

Single-particle-picture breakdown in laterally weakly confining GaAs quantum dots

“…To gather a deeper insight in the experimental results and support our claim that the SP model is not suitable to extract single-particle g-factors from PL measurements, we perform calculations combining the 8-band k·p method for the computation of single-particle states and the CI method for the excitonic states confined in our weakly confining QDs. On the one hand this approach allows a realistic treatment of the QD shape and composition 48,49 , including strain and piezoelectricity up to second order [50][51][52] . On the other hand it allows an intrinsic treatment of correlation effects, which are included in CI 31,49 via the excited SP states used to construct the Slater determinants.…”

“…On the one hand this approach allows a realistic treatment of the QD shape and composition 48,49 , including strain and piezoelectricity up to second order [50][51][52] . On the other hand it allows an intrinsic treatment of correlation effects, which are included in CI 31,49 via the excited SP states used to construct the Slater determinants. This is important, because we expect correlation effects between the confined carriers to play a dominant role in the weak confinement regime.…”

Structural and compositional analysis of (InGa)(AsSb)/GaAs/GaP Stranski–Krastanov quantum dots

“…The erase time strongly depends on the localization energy and the applied bias. The storage time “ τ ” mainly depends on localization energy (depth of the localization potential) and the capture cross-section ( σ ∞ -scattering probability of holes) 30 – 32 . High localization energies with low-capture cross-section are preferred to obtain long storage time.…”

“…Instead, for QDs grown via metal-organic vapor phase epitaxy (MOVPE), the current storage time for pure In 0.5 Ga 0.5 As/GaP QDs is 230 s at room temperature 38 , while an improvement of one order of magnitude was obtained by adding Sb during the QD growth, leading to a record storage time of 1 h at room temperature, as reported by Sala et al 27 , 39 . A complete growth optimization of the (InGa)(AsSb)/GaAs/GaP QDs was reported by Sala et al 26 and a detailed theoretical analysis of the quaternary QD system was published by P. Klenovský et al 32 . The storage time of these QDs was measured utilizing deep-level transient spectroscopy 27 .…”

Crystalline Truncated Micropyramids Grown from GaAs Liquid Phase on GaP (001) Substrates

“…The controlled growth of lattice‐mismatched epitaxial layers with built‐in strains [ 1–5 ] is fundamental to engineer the electronic band structure of semiconductors for the manufacture of optoelectronic devices such as photodiodes, [ 6–8 ] light emitters, [ 9 ] quantum dots, [ 10–12 ] nanowires, [ 13 ] and highly efficient solar cells. [ 14,15 ] In general, in III–V materials, a large lattice mismatch between two materials exists whenever ( a epi – a s ) − a s > 2%, [ 16,17 ] where a epi and a s are the lattice parameters of the epitaxial layer and the substrate, respectively.…”