Study of carrier dynamics in quantum dots under simultaneous optical and electrical excitation
Date Issued
2009
Date
2009
Author(s)
Cheng, Wei-Lin
Abstract
In this thesis, simultaneous optical and electrical excitation is used to study the carrier behaviors of quantum dots. Electrical excitation, serving the purpose of controlling the carrier occupation probability, is used in conjunction with optical excitation to determine the relations between the occupation probability and carrier dynamics. The sample studied in this thesis is a five-layer quantum-dot optical amplifier with tilted facets and windowed stripe on top metal contact.nder high excitation conditions, the instantaneous carrier injection results in a sudden increase in the number of excited carriers captured into higher energy states. Using the time correlated single photon counting (TCSPC) setup, carrier relaxation between energy states can be observed as well as the effect of carrier replenishing. ext, the dependence on excitation intensity that determines the recombination mechanisms of carriers is studied. Exploiting this dependence on excitation intensity, electrical excitation is used to investigate the change in carrier recombination mechanisms by varying injection current. nder low current injection, the ground state and excited states exhibit similar trends of decreasing decay time as injection current is increased. At a higher current injection, however, the ground state demonstrates an injection-independent time constant as opposed to the behavior of the excited state where its time constant increases as current injection increases.he sample studied for this thesis is a five-layer quantum dot (DO1128) “Tilted Windows Laser Structure”.
Subjects
optical excitation
electrical excitation
TCSPC
carrier relaxation
recombination mechanisms
occupation probability
Type
thesis
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