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Intrinsic radiative lifetime derived via absorption cross section of one-dimensional excitons.

Chen S, Yoshita M, Ishikawa A, Mochizuki T, Maruyama S, Akiyama H, Hayamizu Y, Pfeiffer LN, West KW - Sci Rep (2013)

Bottom Line: We experimentally verified our approach for one-dimensional (1D) excitons in high-quality 14 × 6 nm(2) quantum wires by comparing it to the conventional approach.Both independent evaluations showed good agreement with each other and with theoretical predictions.This approach opens a promising path to studying low-dimensional exciton physics.

View Article: PubMed Central - PubMed

Affiliation: Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, Japan. shaoqiangchen@gmail.com

ABSTRACT
Intrinsic radiative lifetime is an essential physical property of low-dimensional excitons that represents their optical transition rate and wavefunction, which directly measures the probability of finding an electron and a hole at the same position in an exciton. However, the conventional method that is used to determine this property via measuring the temperature-dependent photoluminescence (PL) decay time involves uncertainty due to various extrinsic contributions at high temperatures. Here, we propose an alternative method to derive the intrinsic radiative lifetime via temperature-independent measurement of the absorption cross section and transformation using Einstein's A-B-coefficient equations derived for low-dimensional excitons. We experimentally verified our approach for one-dimensional (1D) excitons in high-quality 14 × 6 nm(2) quantum wires by comparing it to the conventional approach. Both independent evaluations showed good agreement with each other and with theoretical predictions. This approach opens a promising path to studying low-dimensional exciton physics.

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Related in: MedlinePlus

Micro-PL and micro-PLE spectra of the 100-period T-shaped quantum wires at 5 K.(a) shows the PL spectrum at an excitation energy of 1.696 eV, illustrating that the emission peak from the T-wires is very sharp and strong; in contrast, the peaks from the arm and stem wells are very weak, indicating that most of the photo-generated carriers flow into the wires rapidly within their lifetime. (b) shows the PLE spectrum of the T-wires at excitation energies from 1.550 eV to 1.696 eV. The energy levels of the T-wire structure are clearly demonstrated, such as the wire state (1.582 eV), wire continuum states (greater than 1.592 eV), arm state (1.603 eV), arm continuum states (greater than 1.620 eV), stem state (1.636 eV), and stem continuum states (greater than 1.660 eV). The right vertical axis measures the absorption rate of the T-wires calibrated by the continuum state of the arm well indicated by the arrow (0.7%). Arb. unit is an abbreviation of arbitrary unit.
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f2: Micro-PL and micro-PLE spectra of the 100-period T-shaped quantum wires at 5 K.(a) shows the PL spectrum at an excitation energy of 1.696 eV, illustrating that the emission peak from the T-wires is very sharp and strong; in contrast, the peaks from the arm and stem wells are very weak, indicating that most of the photo-generated carriers flow into the wires rapidly within their lifetime. (b) shows the PLE spectrum of the T-wires at excitation energies from 1.550 eV to 1.696 eV. The energy levels of the T-wire structure are clearly demonstrated, such as the wire state (1.582 eV), wire continuum states (greater than 1.592 eV), arm state (1.603 eV), arm continuum states (greater than 1.620 eV), stem state (1.636 eV), and stem continuum states (greater than 1.660 eV). The right vertical axis measures the absorption rate of the T-wires calibrated by the continuum state of the arm well indicated by the arrow (0.7%). Arb. unit is an abbreviation of arbitrary unit.

Mentions: Figure 2 shows the micro-PL and micro-PL excitation (PLE) spectra of the samples at 5 K. The strong PL peak of the T-wires was detected at 1.581 eV (Fig. 2a). The Stokes shift (0.7 meV) of the ground state excitons in the T-wires is smaller than the PLE peak width of 2.4 meV, demonstrating the high quality of the T-wires (Fig. 2b). Even though the excitation light at 1.696 eV initially creates excitons in the arm well and stem wells, the PL from the T-wires is dominant in the PL spectrum. This result indicates that most (greater than 90%) of the carriers created in the arm well flow rapidly to adjacent T-wires (Fig. 1b), which supports our assumption that the PLE spectrum in the spectral region of the T-wires and the arm well is proportional to their absorption probability.


Intrinsic radiative lifetime derived via absorption cross section of one-dimensional excitons.

Chen S, Yoshita M, Ishikawa A, Mochizuki T, Maruyama S, Akiyama H, Hayamizu Y, Pfeiffer LN, West KW - Sci Rep (2013)

Micro-PL and micro-PLE spectra of the 100-period T-shaped quantum wires at 5 K.(a) shows the PL spectrum at an excitation energy of 1.696 eV, illustrating that the emission peak from the T-wires is very sharp and strong; in contrast, the peaks from the arm and stem wells are very weak, indicating that most of the photo-generated carriers flow into the wires rapidly within their lifetime. (b) shows the PLE spectrum of the T-wires at excitation energies from 1.550 eV to 1.696 eV. The energy levels of the T-wire structure are clearly demonstrated, such as the wire state (1.582 eV), wire continuum states (greater than 1.592 eV), arm state (1.603 eV), arm continuum states (greater than 1.620 eV), stem state (1.636 eV), and stem continuum states (greater than 1.660 eV). The right vertical axis measures the absorption rate of the T-wires calibrated by the continuum state of the arm well indicated by the arrow (0.7%). Arb. unit is an abbreviation of arbitrary unit.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3672882&req=5

f2: Micro-PL and micro-PLE spectra of the 100-period T-shaped quantum wires at 5 K.(a) shows the PL spectrum at an excitation energy of 1.696 eV, illustrating that the emission peak from the T-wires is very sharp and strong; in contrast, the peaks from the arm and stem wells are very weak, indicating that most of the photo-generated carriers flow into the wires rapidly within their lifetime. (b) shows the PLE spectrum of the T-wires at excitation energies from 1.550 eV to 1.696 eV. The energy levels of the T-wire structure are clearly demonstrated, such as the wire state (1.582 eV), wire continuum states (greater than 1.592 eV), arm state (1.603 eV), arm continuum states (greater than 1.620 eV), stem state (1.636 eV), and stem continuum states (greater than 1.660 eV). The right vertical axis measures the absorption rate of the T-wires calibrated by the continuum state of the arm well indicated by the arrow (0.7%). Arb. unit is an abbreviation of arbitrary unit.
Mentions: Figure 2 shows the micro-PL and micro-PL excitation (PLE) spectra of the samples at 5 K. The strong PL peak of the T-wires was detected at 1.581 eV (Fig. 2a). The Stokes shift (0.7 meV) of the ground state excitons in the T-wires is smaller than the PLE peak width of 2.4 meV, demonstrating the high quality of the T-wires (Fig. 2b). Even though the excitation light at 1.696 eV initially creates excitons in the arm well and stem wells, the PL from the T-wires is dominant in the PL spectrum. This result indicates that most (greater than 90%) of the carriers created in the arm well flow rapidly to adjacent T-wires (Fig. 1b), which supports our assumption that the PLE spectrum in the spectral region of the T-wires and the arm well is proportional to their absorption probability.

Bottom Line: We experimentally verified our approach for one-dimensional (1D) excitons in high-quality 14 × 6 nm(2) quantum wires by comparing it to the conventional approach.Both independent evaluations showed good agreement with each other and with theoretical predictions.This approach opens a promising path to studying low-dimensional exciton physics.

View Article: PubMed Central - PubMed

Affiliation: Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba, Japan. shaoqiangchen@gmail.com

ABSTRACT
Intrinsic radiative lifetime is an essential physical property of low-dimensional excitons that represents their optical transition rate and wavefunction, which directly measures the probability of finding an electron and a hole at the same position in an exciton. However, the conventional method that is used to determine this property via measuring the temperature-dependent photoluminescence (PL) decay time involves uncertainty due to various extrinsic contributions at high temperatures. Here, we propose an alternative method to derive the intrinsic radiative lifetime via temperature-independent measurement of the absorption cross section and transformation using Einstein's A-B-coefficient equations derived for low-dimensional excitons. We experimentally verified our approach for one-dimensional (1D) excitons in high-quality 14 × 6 nm(2) quantum wires by comparing it to the conventional approach. Both independent evaluations showed good agreement with each other and with theoretical predictions. This approach opens a promising path to studying low-dimensional exciton physics.

Show MeSH
Related in: MedlinePlus