Biomedical Engineering Reference
In-Depth Information
Fig. 2.11
TEM image of InP ring-shaped QDMs grown from In thickness 3.2 ML with deposition
rate of 1.6 ML/s at a deposition temperature of 250
◦
C and a crystallization temperature of 200
◦
C
When InP ring-shaped QDMs are excited by blue laser, PL emission at red light
will be detected.
We u s e A r
laser with a 478 nm wavelength and laser power up to 80 mW for
our PL excitation. The sample is set up in a liquid Helium cryostat for cooling down
to 20 K. PL signal is detected by either a CCD detector or a liquid nitrogen cooled
InGaAs detector.
Photoluminescence (PL) is a basic analytical tool in studying the formation of
InP ring-shaped QDMs throughout our whole experiment. InP ring-shaped QDMs
are composed of QD chains on the ring robe. QDs on the ring are self-assembled.
Therefore, they are not uniform in QD size. The difference in QD size leads to a
broad PL spectrum. The PL spectroscopy is used to determine the homogeneity of
the QDs on the ring as well as their crystal quality.
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