Buried island

50'nm

Figure 9. An example of an unburied and two buried Ge/Si(001) islands in a multilayer sample grown by MBE at 575 ° C. The QD boundaries are highlighted with black stars.

where adatoms have sufficient surface mobility, a QD will not be covered by the GaAs until the capping layer thickness reaches the QD height. Then, with the high-temperature deposition at 580 °C, the larger QDs will remain uncapped and so will be sublimed, while the smaller QDs will be protected by the capping layer formed at the lower temperature. In this way, a very narrow QD size distribution was obtained and the QD density was decreased.

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