Lateral Arrangement of Ge Self-Assembled Quantum Dots on a Partially Relaxed Si<sub>x</sub>Ge<sub>1−x</sub> Buffer Layer
Since the observation of pyramidal Ge islands formed on Si (001) by epitaxy in the early 1990s, there has been substantial interest in fabricating dense and uniform arrays of self-assembled Ge quantum dots. This chapter is dedicated to the review of one of several methods used to fabricate laterally ordered arrays of semiconductor structures with 3D quantum confinement, namely, epitaxial growth on partially relaxed SiGe buffer layers.
A convenient technique for creating self-assembled quantum dots is the growth of a strained epitaxial layer to create small islands in a wide range of lattice-mismatched material systems, where the substrate material has a larger band gap than the epitaxial layer. The epitaxy of quantum dots uses the transition from the two-dimensional (2D) layer to three-dimensional (3D) island growth that takes place during the deposition of a pseudomorphically strained epitaxial layer. Heteroepitaxial growth of highly strained structures has attracted interest lately because it offers the possibility of fabricating islands with very narrow size distributions without the need for any substrate patterning or surface treatment. Quantum dot formation has been observed for a wide range of material/substrate combinations, including InAs/GaAs, InGaAs/GaAs, InP/GaAs, SiGe/Si, and Ge/Si. Among all these different material combinations, Ge/Si represents the simplest system.
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