Quantum Confined Stark Shift and Ground State Optical Transition Rate in [100] Laterally Biased InAs/GaAs Quantum Dots

Usman, Muhammad; Ryu, Hoon; Lee, Sunhee; Tan, Yui-Hong Matthias; Klimeck, Gerhard

doi:10.1109/iwce.2009.5091140

Cited by 4 publications

(5 citation statements)

References 32 publications

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“…, where H is single particle tight binding Hamiltonian, E 2or3or4 are electron states, H 1 is the top most valence band hole state, and is position vector along the polarization direction of the incident light [32,[39][40][41]. Figure 3 Figure 3(e) compares the calculated optical strengths from NEMO 3D simulator including the piezoelectric effects with the experimental measurements.…”

Section: With Piezoelectricity  One Anticrossing In the Experimentalmentioning

confidence: 99%

“…, where H is single particle tight binding Hamiltonian, E 2or3or4 are electron states, H 1 is the top most valence band hole state, and is position vector along the polarization direction of the incident light [32,[39][40][41]. Figure 3 , where and are the transition rate intensities of (E 2 ,H 1 ) , (E 3 ,H 1 ) and (E 4 ,H 1 ), respectively corresponding to the figure 3(b) in the experimental field range.…”

Section: With Piezoelectricity  One Anticrossing In the Experimental...mentioning

confidence: 99%

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Quantitative excited state spectroscopy of a single InGaAs quantum dot molecule through multi-million-atom electronic structure calculations

Usman¹,

Tan²,

Ryu³

et al. 2011

Nanotechnology

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Atomistic electronic structure calculations are performed to study the coherent inter-dot couplings of the electronic states in a single InGaAs quantum dot molecule. The experimentally observed excitonic spectrum by H. Krenner et al. [12] is quantitatively reproduced, and the correct energy states are identified based on a previously validated atomistic tight binding model. The extended devices are represented explicitly in space with 15 million atom structures. An excited state spectroscopy technique is applied where the externally applied electric field is swept to probe the ladder of the electronic energy levels (electron or hole) of one quantum dot through anti-crossings with the energy levels of the other quantum dot in a two quantum dot molecule. This technique can be used to estimate the spatial electron-hole spacing inside the quantum dot molecule as well as to reverse engineer quantum dot geometry parameters such as the quantum dot separation. Crystal deformation induced piezoelectric effects have been discussed in the literature as minor perturbations lifting degeneracies of the electron excited (P and D) states, thus affecting polarization alignment of wave function lobes for III-V Heterostructures such as single InAs/GaAs quantum dots. In contrast this work demonstrates the crucial importance of piezoelectricity to resolve the symmetries and energies of the excited states through matching the experimentally measured spectrum in an InGaAs quantum dot molecule under the influence of an electric field. Both linear and quadratic piezoelectric effects are studied for the first time for a quantum dot molecule and demonstrated to be indeed important. The net piezoelectric contribution is found to be critical in determining the correct energy spectrum, which is in contrast to recent studies reporting vanishing net piezoelectric contributions.

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Section: With Piezoelectricity  One Anticrossing In the Experimentalmentioning

confidence: 99%

“…, where H is single particle tight binding Hamiltonian, E 2or3or4 are electron states, H 1 is the top most valence band hole state, and is position vector along the polarization direction of the incident light [32,[39][40][41]. Figure 3 , where and are the transition rate intensities of (E 2 ,H 1 ) , (E 3 ,H 1 ) and (E 4 ,H 1 ), respectively corresponding to the figure 3(b) in the experimental field range.…”

Section: With Piezoelectricity  One Anticrossing In the Experimental...mentioning

confidence: 99%

Quantitative excited state spectroscopy of a single InGaAs quantum dot molecule through multi-million-atom electronic structure calculations

Usman¹,

Tan²,

Ryu³

et al. 2011

Nanotechnology

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“…The atoms at the surface are passivated according to our published approach. 36 The inter-band optical transition strengths between the electron-hole energy states are computed using Fermi's golden rule by squared absolute value of the momentum matrix elements summed over spin degenerate states: 41,52 …”

Section: Electronic and Optical Spectramentioning

confidence: 99%

In-plane polarization anisotropy of ground state optical intensity in InAs/GaAs quantum dots

Usman¹

2011

Journal of Applied Physics

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The design of optical devices such as lasers and semiconductor optical amplifiers for telecommunication applications requires polarization insensitive optical emissions in the region of 1500 nm. Recent experimental measurements of the optical properties of stacked quantum dots have demonstrated that this can be achieved via exploitation of inter-dot strain interactions. In particular, the relatively large aspect ratio (AR) of quantum dots in the optically active layers of such stacks provide a two-fold advantage, both by inducing a red shift of the gap wavelength above 1300 nm, and increasing the TM001-mode, thereby decreasing the anisotropy of the polarization response. However, in large aspect ratio quantum dots (AR > 0.25), the hole confinement is significantly modified compared with that in lower AR dots-this modified confinement is manifest in the interfacial confinement of holes in the system. Since the contributions to the ground state optical intensity (GSOI) are dominated by lower-lying valence states, we therefore propose that the room temperature GSOI be a cumulative sum of optical transitions from multiple valence states. This then extends previous theoretical studies of flat (low AR) quantum dots, in which contributions arising only from the highest valence state or optical transitions between individual valence states were considered. The interfacial hole distributions also increases in-plane anisotropy in tall (high AR) quantum dots (TE110 not equal TE-110), an effect that has not been previously observed in flat quantum dots. Thus, a directional degree of polarization (DOP) should be measured (or calculated) to fully characterize the polarization response of quantum dot stacks. Previous theoretical and experimental studies have considered only a single value of DOP: either [110] or [-110]. (C) 2011 American Institute of Physics. [doi:10.1063/1.3657783

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“…For a typical single InAs QD, the T rans e dependence on the electric field is parabolic [29,51], indicating a large magnitude for the polarizibility β and a very small magnitude for the dipole moment ρ -a direct consequence of the small space available for the electron and hole separation. For QD stacks, made up of a large number of QD layers, electric fields are capable of pushing electron and hole wave functions far away from each other (even at the opposite ends of the stack for large fields), and therefore can lead to large separations between the electron and hole wave functions.…”

Section: − Transition Energies and Band-gap Wavelengthsmentioning

confidence: 99%

“…Such fields are either present internally such as investigated recently for the solar cells [25,26], or can be applied externally to purposely tune the properties of the devices for a certain operation [14]. Although the impact of electric fields has been extensively studied in the literature for the single QDs [27][28][29], the bi-layer QDMs [7,[30][31][32][33][34], and for the small QD stacks consisting of three to four QD layers [35], to-date no theoretical understanding is available on the electronic and optical properties of the multi-layer QDMs under the influence of electrical fields.…”

Section: − Introductionmentioning

confidence: 99%

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

Usman

2015

Nanoscale

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Strongly-coupled quantum dot molecules (QDMs) are widely deployed in the design of a variety of optoelectronic, photovoltaic, and quantum information devices. An efficient and optimized performance of these devices demands engineering of the electronic and optical properties of the underlying QDMs. The application of electric fields offers a knob to realise such control over the QDM characteristics for a desired device operation. We perform multi-million-atom atomistic tight-binding calculations to study the influence of electric fields on the electron and hole wave function confinements and symmetries, the ground-state transition energies, the band-gap wavelengths, and the optical transition modes. The electrical fields both parallel ( E p ) and anti-parallel ( E a ) to the growth direction are investigated to provide a comprehensive guide on the understanding of the electric field effects. The strain-induced asymmetry of the hybridized electron states is found to be weak and can be balanced by applying a small E a electric field, of the order of 1 KV/cm. The strong interdot couplings completely break down at large electric fields, leading to single QD states confined at the opposite edges of the QDM. This mimics a transformation from a type-I band structure to a type-II band structure for the QDMs, which is a critical requirement for the design of intermediate-band solar cells (IBSC). The analysis of the field-dependent ground-state transition energies reveal that the QDM can be operated both as a high dipole moment device by applying large electric fields and as a high polarizibility device under the application of small electric field magnitudes. The quantum confined Stark effect (QCSE) red shifts the band-gap wavelength to 1.3 µm at the 15 KV/cm electric field; however the reduced electron-hole wave function overlaps lead to a decrease in the interband optical transition strengths by roughly three orders of magnitude. The study of the polarisation-resolved optical modes indicate the benefit of applying small electric fields, which lead to an isotropic polarisation response, a desirable property for the semiconductor optical amplifiers (SOAs).1 arXiv:1508.05981v1 [cond-mat.mes-hall]

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Quantum Confined Stark Shift and Ground State Optical Transition Rate in [100] Laterally Biased InAs/GaAs Quantum Dots

Cited by 4 publications

References 32 publications

Quantitative excited state spectroscopy of a single InGaAs quantum dot molecule through multi-million-atom electronic structure calculations

Quantitative excited state spectroscopy of a single InGaAs quantum dot molecule through multi-million-atom electronic structure calculations

In-plane polarization anisotropy of ground state optical intensity in InAs/GaAs quantum dots

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

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