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SUMMARY:Molecular Beam Epitaxial overgrowth on pre-patterned substrates - 
 Dr. Paola Atkinson (SP Group\, Cavendish Laboratory)
DTSTART:20060515T131500Z
DTEND:20060515T141500Z
UID:TALK4949@talks.cam.ac.uk
CONTACT:K DAS GUPTA
DESCRIPTION:Molecular beam epitaxy is a method of depositing layers of hig
 h purity\ncrystalline material on a substrate with a high degree of accura
 cy over the\nlayer thickness. By suitable choice of materials\, the bandst
 ructure can be\nengineered to confine carriers to within a few nanometers 
 in the growth\ndirection. Confinement in all three dimensions can be achie
 ved by the growth\nof lattice-mismatched materials where\, under suitable 
 growth conditions\, the\nbuild-up of strain in the overlying material can 
 cause small 3D islands\,\nknown as self-assembled quantum dots\, to form s
 pontaneously.\n\nThe use of pre-patterned substrates has several advantage
 s. One advantage is\na strictly geometric one as some device geometries\, 
 such as a lateral p-n\njunction\, or a patterned back-gate\, are not possi
 ble in a single growth step\non a planar surface. Pre-patterning can also 
 lead to lateral confinement\nwithout the need for post-growth patterning d
 ue to different growth rates on\ndifferent facets introducing lateral vari
 ations in the thickness of the\novergrown material. Pre-patterning can als
 o be used to control the\nnucleation site of self-assembled quantum dots b
 y changing the underlying\nstep density or the underlying strain on the su
 bstrate. This control of the\nquantum dot site is of crucial importance fo
 r the integration of quantum\ndots in photonic cavity structures and will 
 be discussed in some detail.\n
LOCATION:Mott Seminar Room\, Cavendish Laboratory\, Department of Physics
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