Epitaxial Growth of III-V Compound Semiconductors
We use molecular beam epitaxy (MBE) to 'grow' III-V compound semiconductors. Shown below is a simplified schematic of the Gen930 MBE chamber we use to grow our samples. A substrate (often referred to as a wafer) is heated while facing a shooting gallery of heated material sources. These sources deliver a semi-columnar molecular beam directed at the substrate. By controlling the substrate temperature and the arrival rate of the molecular beams we can ensure a semiconductor crystal will grow buy bonding together with the substrate surface and each other to form compounds such as Gallium Arsenide, Indium Arsenide, Gallium Antimonide, and a host of other materials.
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Below to the right is a listing of the Group III sources (Gallium x2, Aluminium, Indium) and Group V sources (Arsenic, Antimony, Bismuth). There are also dopant sources for Beryllium, Tellurium, and filament sources for Silicon and Carbon. Recently we have installed a BandiT temperature measurement system from k-Space Associates to allow us improved temperature monitoring of our substrates.
MBE allows for exquisite control over growth rates and interface formation. A key in-situ diagnostic tool is Reflective High Energy Electron Diffraction (RHEED) that comes as standard on MBE systems. RHEED allows you to not only directly observe the growth process and tune growth rates, but also gives direct information on the growth surface. The two movies shown below illustrate this feature. On the left is the case for the surface arrangement of atoms changing for Gallium Arsenide. On the right is the RHEED pattern when Indium Arsenide if grown on Gallium Arsenide, due to the differences in how far apart the atoms in these two compounds like to be (referred to as lattice strain) the Indium Arsenide will 'ball up' on the surface, forming small pimple like features. These pimples act as 'quantum dots' with novel, tunable properties and are an area of vast research interest. In the RHEED pattern that develops we see the formation of chevrons as a telltale sign we have formed the Indium Arsenide quantum dots.
Some Articles Related to Epitaxial Growth
Sb dissociative surface coverage model for incorporation of antimony in GaAsSb layers grown on GaAs (0 0 1) substrates
Z. Zhang, K. Ghosh, N. N. Faleev, H. Wang, C. B. Honsberg, P. Reece, S. P. Bremner
Journal of Crystal Growth, 526, 125231, 2019
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Impact of stress relaxation in GaAsSb cladding layers on quantum dot creation in InAs/GaAsSb structures grown on GaAs (001)
S. P. Bremner, K. Y. Ban, N. N. Faleev, C. B. Honsberg, D. J. Smith
Journal of Applied Physics, 114, (10), 103511, 2013
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Use of a GaAsSb buffer layer for the formation of small, uniform, and dense InAs quantum dots
K. Y. Ban, S. P. Bremner, G. Liu, S. N. Dahal, P. C. Dippo, A. G. Norman, C. B. Honsberg
Applied Physics Letters, 96(18), 183101,2010
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