Advanced Fabrication Techniques for Type-II Superlattice VLWIR Detectors

The growth and fabrication of nanostructures, particularly short period Type-II superlattices, rely on high quality crystalline materials. Defects and non-planarities on the substrate surface and non-uniformities in the epitaxial layers can impair device performance. Gallium antimonide (GaSb) substrates have utility in exploring new III-V alloys and devices. While GaSb substrates are available, shipment volume pales in comparison to other III-V substrates such as GaAs and InP. As such, production and preparation of GaSb wafers is far from refined. Surface and growth non-uniformities remain an issue with these substrates. In an effort to solve this problem, we propose to investigate and adopt a two-step approach. First is a novel in situ polishing technique. The surface of GaSb wafers will be polished and cleaned prior to epitaxial growth, and the smooth wafer surface will remain free of atmospheric contamination until semiconductor deposition is complete. Second is a method to reduce contamination of the epilayers from undesired molecular species. Once these techniques are proven viable, the apparatuses can be redesigned with minimal changes and retrofitted to epitaxial systems already deployed in the field.