InP Ring-Shaped Quantum Dot Molecules by Droplet Epitaxy - Quantum Dot Molecules - page 38

Fig. 2.7 In droplets are transformed to InP QRs and InP ring-shaped QDMs when more indium
thickness is supplied from 1.6 to 6.4 ML during the deposition process. The deposition temperature
and crystallization temperature are fixed at 250 and 200 ◦ C, respectively
When growth conditions at the deposition step are optimized and fixed like In
thickness, In deposition rate and deposition temperature, in the next consecutive
step of crystallization, InP ring-shaped QDMs will be affected by the crystallization
temperature. At higher crystallization temperature, the ring diameter is longer but
the QDM density and the number of QDs per QDM are smaller. Figure 2.10 shows
the experimental results when crystallization temperature is varied from 150 to
300 ◦ C (deposition temperature 250 ◦ C, deposition rate 0.8 ML/s, indium thickness
3.2 ML). However, the effect of crystallization temperature on InP ring-shaped
QDMs formation seems to be a secondary one. No large change in the nanostructure