Abstract
The dynamics of electron capture and relaxation in an n-doped quantum-dot (QD) infrared detector structure are studied directly in the time domain using ultrafast intraband-pump-interband-probe differential transmission spectroscopy. Femtosecond midinfrared pulses are used to excite electrons from the doped QDs into the conduction band continuum, and the complete electron distribution functions are monitored as a function of time using an interband probe. Because only electrons are excited and no holes are present, the electron-hole scattering which dominates the relaxation in bipolar systems is not present, and the measurement yields the electron dynamics exclusively. Excitation-dependent electron capture times were measured from 40 to <10ps with increasing pump intensity. Intradot inter-level relaxation times were observed to be ∼ 100 ps, driven by Auger-type electron-electron scattering. Nanosecond-scale dynamics in the n=1 state were also observed and attributed to transport effects. Our results indicate that the phonon bottleneck in the QDs is circumvented by Auger scattering; nevertheless, the electron dynamics in the unipolar device are found to be slower than those observed in bipolar systems, which confirms the significance of the holes in the carrier relaxation in bipolar devices. The results also support the improved operation of QD infrared photodetectors relative to quantum-well-based devices.
| Original language | English |
|---|---|
| Pages (from-to) | 486-496 |
| Number of pages | 11 |
| Journal | IEEE Journal of Quantum Electronics |
| Volume | 43 |
| Issue number | 6 |
| DOIs | |
| Publication status | Published - 2007 Jun 1 |
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All Science Journal Classification (ASJC) codes
- Atomic and Molecular Physics, and Optics
- Condensed Matter Physics
- Electrical and Electronic Engineering
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Ultrafast electronic dynamics in unipolar n-doped InGaAs-GaAs self-assembled quantum dots. / Wu, Zong Kwei; Choi, Hyunyong; Su, Xiaohua; Chakrabarti, Subhananda; Bhattacharya, Pallab; Norris, Theodore B.
In: IEEE Journal of Quantum Electronics, Vol. 43, No. 6, 01.06.2007, p. 486-496.Research output: Contribution to journal › Article
TY - JOUR
T1 - Ultrafast electronic dynamics in unipolar n-doped InGaAs-GaAs self-assembled quantum dots
AU - Wu, Zong Kwei
AU - Choi, Hyunyong
AU - Su, Xiaohua
AU - Chakrabarti, Subhananda
AU - Bhattacharya, Pallab
AU - Norris, Theodore B.
PY - 2007/6/1
Y1 - 2007/6/1
N2 - The dynamics of electron capture and relaxation in an n-doped quantum-dot (QD) infrared detector structure are studied directly in the time domain using ultrafast intraband-pump-interband-probe differential transmission spectroscopy. Femtosecond midinfrared pulses are used to excite electrons from the doped QDs into the conduction band continuum, and the complete electron distribution functions are monitored as a function of time using an interband probe. Because only electrons are excited and no holes are present, the electron-hole scattering which dominates the relaxation in bipolar systems is not present, and the measurement yields the electron dynamics exclusively. Excitation-dependent electron capture times were measured from 40 to <10ps with increasing pump intensity. Intradot inter-level relaxation times were observed to be ∼ 100 ps, driven by Auger-type electron-electron scattering. Nanosecond-scale dynamics in the n=1 state were also observed and attributed to transport effects. Our results indicate that the phonon bottleneck in the QDs is circumvented by Auger scattering; nevertheless, the electron dynamics in the unipolar device are found to be slower than those observed in bipolar systems, which confirms the significance of the holes in the carrier relaxation in bipolar devices. The results also support the improved operation of QD infrared photodetectors relative to quantum-well-based devices.
AB - The dynamics of electron capture and relaxation in an n-doped quantum-dot (QD) infrared detector structure are studied directly in the time domain using ultrafast intraband-pump-interband-probe differential transmission spectroscopy. Femtosecond midinfrared pulses are used to excite electrons from the doped QDs into the conduction band continuum, and the complete electron distribution functions are monitored as a function of time using an interband probe. Because only electrons are excited and no holes are present, the electron-hole scattering which dominates the relaxation in bipolar systems is not present, and the measurement yields the electron dynamics exclusively. Excitation-dependent electron capture times were measured from 40 to <10ps with increasing pump intensity. Intradot inter-level relaxation times were observed to be ∼ 100 ps, driven by Auger-type electron-electron scattering. Nanosecond-scale dynamics in the n=1 state were also observed and attributed to transport effects. Our results indicate that the phonon bottleneck in the QDs is circumvented by Auger scattering; nevertheless, the electron dynamics in the unipolar device are found to be slower than those observed in bipolar systems, which confirms the significance of the holes in the carrier relaxation in bipolar devices. The results also support the improved operation of QD infrared photodetectors relative to quantum-well-based devices.
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U2 - 10.1109/JQE.2007.897864
DO - 10.1109/JQE.2007.897864
M3 - Article
AN - SCOPUS:34249950391
VL - 43
SP - 486
EP - 496
JO - IEEE Journal of Quantum Electronics
JF - IEEE Journal of Quantum Electronics
SN - 0018-9197
IS - 6
ER -