Biomedical Engineering Reference
In-Depth Information
Fig. 2.17
Temperature dependence of PL emission from InP ring-shaped QDMs
2.6
Number of QDs per Ring and Potential Applications
of InP Ring-Shaped QDMs
The growth parameters can modify QRs to ring-shaped QDMs. With limited volume
of In thickness less than 1.6 ML, only QRs are realized. Increase in In deposition
under appropriate crystallization condition with P pressure, InP QDs are created on
the ring robe. The critical thickness for QD formation on the ring robe is in the range
of 1.6-3.2 ML.
At a deposition temperature of 250
◦
C and a crystallization temperature of 200
◦
C,
when In deposition rate of 1.6 ML/s and with In coverage of 3.2 ML, 46% of InP
ring-shaped QDMs have eight dots per ring. These octa-QDMs are an interesting
feature for extended quantum cellular automata application as shown in Fig.
2.18
.
The basic idea of QCA is based on two electrons being located in quadra quantum
dot set in diagonal positions due to Coulomb repulsion. The position of this electron
pair can be either left or right diagonal configuration which represents either “1” or
“0” in the binary system.
In octa QDMs having eight QDs per cell, the electron pair will have more
stable positions, i.e., two diagonal configurations and more vertical and horizontal
configurations. The EQCA gives more logic encodings as “1”, “0”, “
+
1/2,” and
“
1/2”. This would enable QDMs to be utilized in future sophisticated quantum
memory and computation.
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