Study of Ultrafast Exciton Dynamics in Zinc-Oxide with Time-Resolved Photoluminescence Spectroscopy
Date Issued
2005
Date
2005
Author(s)
Jen, Fang-Yi
DOI
en-US
Abstract
In this research, we systematically investigate the optical properties in a
ZnO thin film. First, we compare the photoluminescence spectrum and
temperature-dependent PL decay time of FX and D0X in ZnO samples of
different morphologies. PL spectra indicate that growth at lower pressures in
MOCVD may enhance the incorporation of acceptors in ZnO and hence lead
to a shorter lifetime in TRPL calibration. The lack of lower-energy
impurity-related emission in high-pressure growth implies the high quality
characteristic of the ZnO thin film. This leads to the long lifetime of FX in
thin film due to the exciton radiative lifetime nature over the thermal
quenching effect.
Second, for further understanding the optical properties of excitonic
manybody interaction under high excitation, we observe not only the
emission line (the M line) of XX, but also that (the D0M line) of
donor-bound biexciton (D0XX) in the excitation-power dependent
measurement. The calibrated two-stage decay times are used to build the
model of ultrafast biexciton dynamics in such a ZnO sample. The interplay
between free exciton (FX), donor-bound exciton (D0X), biexciton (XX) and
donor-bound biexciton (D0XX) in ZnO will be discussed. We explain the
trends of the calibrated decay times successfully with a four-level model.
III
Finally, the radiative lifetime of the mixed system of FX and D0X is
calibrated based on the thermal quenching rate of the integrated PL intensity
of the system. With the radiative lifetime data, the FX radiative lifetimes are
estimated by using a theoretical relation between the lifetime and the
spectral width. From the results of FX radiative lifetime, we also calibrate
the D0X radiative lifetimes. The results support our model that the D0X
radiative behavior is similar to that of FX when the thermal energy is smaller
than the donor binding energy.
Subjects
激子
氧化鋅
exciton
ZnO
Type
thesis
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