100mm diameter GaSb substrates with extended IR wavelength for advanced space-based applications

摘要

A key component for third generation FPA development is the megapixel strain layer superlattice (SLS) structures on GaSb substrates for advanced infrared detectors. A significant aspect that inhibits widespread application of large format device growth on GaSb is the starting substrate size. Recently, the Czochralski method resulted in the world's first 100mm GaSb boules. The 100mm GaSb substrates can be ultra-low doped (n~4-9x1015/cm3) for extended IR wavelength transparency. A plethora of changes to the manufacturing process is required for consistent 100mm GaSb growth and substrate polishing. In this study, we examined the surface quality of the 100mm GaSb as a function of a standard and experimental Polish "A" which incorporated an additional CMP step as well as a longer final polish time. Atomic force microscopy (AFM) and power spectral density (PSD) as a function of polish process measured the surface morphology. Interferometry was used to analyze free standing wafer flatness. Electron spectroscopy for chemical analysis (ESCA) determined surface oxide thickness, and successful MBE growth of a 400 period Complimentary Barrier Infrared Detector (CBIRD) structure assessed SLS based device suitability. The epi structure was examined by x-ray diffraction (XRD). The low 0.3-0.4nm Ra starting 100mm GaSb roughness values, the wafer flatness ~2.3μm per 16 wafer batch, the low FWHM SLo = 15.48 arsec of the successful CBIRD epi growth and related high intensity XRD ~6.6nm periodicity peaks suggest that the modified polish provides the 100mm GaSb with a desirable epi ready character and excellent surface crystallinity for advanced IRFPA applications