Large diameter 'ultra-flat' epitaxy ready GaSb substrates: requirements for MBE grown advanced infrared detectors

In this paper we describe the crystal growth and surface characterisation of 'ultra-flat' 4" GaSb substrates suitable for the epitaxial deposition of advanced infrared detectors. Results will be presented on the production of single crystal 4" GaSb ingots grown by a modified version of the liquid encapsulated Czochralski (LEC) technique, supported by the analysis of bulk material quality by dislocation etch pit density assessments. This study will also describe how various techniques were used to characterize the quality of the bare substrate. Surface properties of the GaSb substrates will be characterized by spectroscopic ellipsometry, white light interferometry and haze/particle defect mapping. Bow, Warp and Total Thickness Variation (TTV) data will be presented for batches of 4" wafers processed on a volume multiwafer-type polishing platform. This study will conclude with a 'blueprint' for the manufacture of large diameter GaSb substrates, this defining the requirements for the production use of GaSb within a commercial epitaxial wafer foundry.

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