Study of carrier relaxation process in quantum dot and quantum well structures by using ultrafast measurement techniques
Date Issued
2010
Date
2010
Author(s)
Wu, Yi-Da
Abstract
In this thesis, we use ultrafast measurement system to study quantum dots carrier dynamics in quantum dots.
The influence of excitation power on capture mechanisms is studied by using an up-conversion measurement system. From the measurement at temperatures varying from 78 K to 235 K, we show that the different capture mechanisms have different temperature dependencies.
To study the effect of carrier occupation probability, a CW green laser light source, serving the purpose of controlling the carrier occupation probability, is used in conjunction with femto-second optical pulse excitation to determine the relations between the occupation probability and carrier dynamics. From the photoluminescence spectrum, under high-intensity excitation, we can find the band filling effect
that corresponds to carrier capture time increase with increasing carrier occupation probability.
Using InAs quantum dots as a stressor changes the GaAsSb quantum well band structure which forms a similar band structure as quantum dots, and alters the carrier dynamics behavior in the quantum well. In different GaAs spacer thickness samples, we discover the phenomenon that carriers, captured by quantum dots, tunnel into quantum wells.
Subjects
quantum dot
quantum well
capture time
Type
thesis
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