MBE growth and characterization of type-II InAs/GaSb superlattices for mid-infrared detection

Type-II InAs/GaSb superlattices (SLs) made of 10 InAs monolayers (MLs) and 10 GaSb MLs, designed to have a cut-off wavelength of 5.4 μm, have been grown on GaSb substrates by solid source molecular beam epitaxy (MBE). In order to obtain lattice-matched structures, a thin layer of InSb was inserted at the GaSb on InAs interface. We demonstrate that structural and optical properties of such structures strongly depend on the thickness of the InSb inserted layer. Strain-balanced InAs/GaSb SLs could be grown, after optimizing the MBE shutter sequence, by using a growth temperature of 390 °C and an inserted InSb layer of thickness 1 ML. Non-optimized pin diodes using 100 periods of such an SL as absorbing material showed an absorption coefficient varying from 4×103 to 6×103 cm−1 at room temperature in the 3-5 μm mid-infrared wavelength region, and a photovoltaic response up to 230 K.