In recent years, the growth of Ge/Si quantum dots (QD) has received growing interest due to the possibility for the realisation of novel QD-based electronic and optoelectronic devices. The most widely used technique to produce Ge/Si QD is based on strain-induced growth mode transition from two-dimensional (2D) to islanding growth (3D) in a highly lattice-mismatched heteroepitaxial system (Stranski-Krastanov growth). However, in view of applications of such quantum dots one of the major drawbacks is their random distribution over the substrate surface.
In this work, we study selective epitaxial growth (SEG) of Ge QD on patterned Si(001) substrates. The formation of Ge/Si QD both in single and stacking layers will be reported. For a single layer, it is shown that the growth of Si buffer layers can greatly affect the formation of Ge/Si QD. By controlling the height of the Si buffer layers, we can obtain only one dot per circular window and a high cooperative arrangement of dots on a striped window with a constant period of 80 nm. In stacking layers, we show that the vertical ordering and also the dot homogeneity can be controlled through the adjustment of the Si spacer-layer thickness.
The optical properties of these structures measured by photoluminescence spectroscopy (PL) will be also reported. In comparison with self-assembled QD, we observed, both in single and stacking layers, the absence of the wetting-layer component, confirming therefore the dot formation by selective growth. First electrical characterizations by means of current-voltage (I-V)measurements of Schottky diodes in the temperature range between 95 and 300K will be presented.
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