Band structure engineering of type-II GaSb/GaAs quantum rings for intermediate band solar cells

Arkani, Reza; Broderick, Christopher A.; O’Reilly, Eoin P.

doi:10.1109/nusod.2019.8807051

Cited by 1 publication

(1 citation statement)

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“…Our numerical analysis of the electronic properties of GaAs 1−x Sb x /GaAs QRs is based on multi-band k•p calculations. 28 We employ a supercell approach, by embedding a cylindrical GaAs 1−x Sb x /GaAs QR in a GaAs matrix, and relax the supercell by minimising the total elastic energy with respect to the components ij of the strain tensor to obtain the strain fields ij (r). The QR VB eigenstates are computed using a strain-dependent 6-band k•p Hamiltonian -i.e.…”

Section: B Numerical: Multi-band K•p Calculationsmentioning

confidence: 99%

Electronic properties of type-II $$\hbox {GaAs}_{1-x} \hbox {Sb}_{x}$$/GaAs quantum rings for applications in intermediate band solar cells

2020

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We present a theoretical analysis of the electronic properties of type-II GaAs1−xSbx/GaAs quantum rings (QRs), from the perspective of applications in intermediate band solar cells (IBSCs). We outline the analytical solution of Schrödinger's equation for a cylindrical QR of infinite potential depth, and describe the evolution of the QR ground state with QR morphology. Having used this analytical model to elucidate general aspects of the electronic properties of QRs, we undertake multiband k•p calculations -including strain and piezoelectric effects -for realistic GaAs1−xSbx/GaAs QRs. Our k•p calculations confirm that the large type-II band offsets in GaAs1−xSbx/GaAs QRs provide strong confinement of holes, and further indicate the presence of resonant (quasi-bound) electron states which localise in the centre of the QR. From the perspective of IBSC design the calculated electronic properties demonstrate several benefits, including (i) large hole ionisation energies, mitigating thermionic emission from the intermediate band, and (ii) electron-hole spatial overlaps exceeding those in conventional GaAs1−xSbx/GaAs QDs, with the potential to engineer these overlaps via the QR morphology so as to manage the trade-off between optical absorption and radiative recombination. Overall, our analysis highlights the flexibility offered by the QR geometry from the perspective of band structure engineering, and identifies specific combinations of QR alloy composition and morphology which offer optimised sub-band gap energies for QR-based IBSCs.

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Section: B Numerical: Multi-band K•p Calculationsmentioning

confidence: 99%