Material and device characterization of Type-II InAs/GaSb superlattice infrared detectors

This work investigates midwave infrared Type-II InAs/GaSb superlattice (SL) grown by molecular beam epitaxy on GaSb substrate. In order to compensate the natural tensile strain of the InAs layers, two different shutter sequences have been explored during the growth. The first one consists of growing an intentional InSb layer at both interfaces (namely GaSb-on-InAs and InAs-on-GaSb interfaces) by migration enhanced epitaxy while the second uses the antimony-for-arsenic exchange to promote an 'InSb-like' interface at the GaSb-on-InAs interface. SLs obtained via both methods are compared in terms of structural, morphological and optical properties by means of high-resolution x-ray diffraction, atomic force microscopy and photoluminescence spectroscopy. By using the second method, we obtained a nearly strain-compensated SL on GaSb with a full width at half maximum of 56 arcsec for the first-order SL satellite peak. Relatively smooth surface has been achieved with a root mean square value of about 0.19 nm on a 2 µm × 2 µm scan area. Finally, a p-i-n device structure having a cut-off wavelength of 5.15 µm at 77 K has been demonstrated with a dark-current level of 8.3 × 10−8 A/cm2 at −50 mV and a residual carrier concentration of 9.7 × 1014 cm−3, comparable to the state-of-the-art.