A study of the preparation of epitaxy-ready polished surfaces of (100) Gallium Antimonide substrates demonstrating ultra-low surface defects for MBE growth
2016
Gallium Antimonide (GaSb) is an important Group III-V compound semiconductor which is suitable for use in
the manufacture of a wide variety of optoelectronic devices such as infra-red (IR) focal plane detectors. A
significant issue for the commercialisation of these products is the production of epitaxy ready GaSb, which
remains a challenge for the substrate manufacturer, as the stringent demands of the MBE process, requires a
high quality starting wafer. In this work large diameter GaSb crystals were grown by the Czochralski (Cz)
method and wafers prepared for chemo-mechanical polishing (CMP). Innovative epi-ready treatments and
novel post polish cleaning methodologies were applied. The effect of these modified finishing chemistries on
substrate surface quality and the performance of epitaxially grown MBE GaSb IR detector structures were
investigated. Improvements in the lowering of surface defectivity, maintaining of the surface roughness and
optimisation of all flatness parameters is confirmed both pre and post MBE growth. In this paper we also discuss
the influence of bulk GaSb quality on substrate surface performance through the characterisation of epitaxial
structures grown on near zero etch pit density (EPD) crystals. In summary progression and development of
current substrate polishing techniques has been demonstrated to deliver a consistent improved surface on GaSb
wafers with a readily desorbed oxide for epitaxial growth.
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