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Molecular Beam Epitaxial overgrowth on pre-patterned substrates

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Molecular beam epitaxy is a method of depositing layers of high purity crystalline material on a substrate with a high degree of accuracy over the layer thickness. By suitable choice of materials, the bandstructure can be engineered to confine carriers to within a few nanometers in the growth direction. Confinement in all three dimensions can be achieved by the growth of lattice-mismatched materials where, under suitable growth conditions, the build-up of strain in the overlying material can cause small 3D islands, known as self-assembled quantum dots, to form spontaneously.

The use of pre-patterned substrates has several advantages. One advantage is a strictly geometric one as some device geometries, such as a lateral p-n junction, or a patterned back-gate, are not possible in a single growth step on a planar surface. Pre-patterning can also lead to lateral confinement without the need for post-growth patterning due to different growth rates on different facets introducing lateral variations in the thickness of the overgrown material. Pre-patterning can also be used to control the nucleation site of self-assembled quantum dots by changing the underlying step density or the underlying strain on the substrate. This control of the quantum dot site is of crucial importance for the integration of quantum dots in photonic cavity structures and will be discussed in some detail.

This talk is part of the Semiconductor Physics series.

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