Ultra-fast Carrier Relaxation in Self-assembled 1.24 Micron-wavelength InAs/GaAs quantum dots
Abstract
Room temperature CW photoluminescence (PL) measurements on self-assembled InAs/GaAs quantum dots show the ground state and excited state emissions around 1.24 micron and 1.14 micron respectively for all excitation levels investigated. This observation is also consistent with our theoretical K*P calculation of the existence of one electron state and two hole states. It's also interesting to notice a more intense PL from the excited state for all excitations. Time-resolved PL measurements on both states were also performed at room temperature to study the carrier dynamics. While the PL for both states has a comparable rise time of 5 ps in high excitations, the ground state rise time is 24 ps in low excitations, 3 times longer than that of the excited state. Ref. [1] has reported optical phonon energies of 29.6, 32.6, and 37.6 meV in InAs/GaAs QDs. Given an energy spacing of 87 meV, carrier relaxation would require multiple phonons. The observed results are suggestive of a phonon bottleneck and cascaded relaxation in low excitations. In high excitations, although a phonon bottleneck still persists, relaxation through carrier-carrier scattering dominates. [1] R. Heitz, et al. Phys. Rev. B Vol. 56, 10435(1997).
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2003
- Bibcode:
- 2003APS..MARK25009Z