Influence of V/III flux ratio on type-II InAs/GaSb superlattice for very-long wavelength

A study was conducted to develop InAs/GaSb type-II superlattices (T2SLs) for very long wavelength infrared detection. The results showed that the V/III flux ratio not only affected the magnitude of the strain but also greatly influenced the surface roughness. By further optimizing the V/III ratio, a sample with a surface roughness of 0.1 nm was obtained within the 5 × 5 μm2 range, and the full width at half maximum (FWHM) of the 0th order peak was only 22.1 arcsec. Through high-resolution transmission electron microscopy (HRTEM) characterization, InAs and GaSb could be effectively distinguished, and strain maps revealed that both interfaces were under large tensile strain. Furthermore, energy dispersive spectroscopy (EDS) testing revealed some degree of intermixing between different layers. Finally, a photoluminescence (PL) spectrum was used to measure the band gap and quality of the superlattice. The PL peak was determined to be 13.65 μm with an FWHM of 27 meV, laying the foundation for the subsequent preparation of a very long wavelength array detector.