Molecular beam epitaxy growth and optical properties of high bismuth content GaSb1-xBix thin films

Epitaxial growth of GaSb1-xBix thin films on GaSb (100) substrates were studied by varying V/III ratio, growth temperatures and Bi flux using molecular beam epitaxy. It is demonstrated that reducing the V/III ratio facilitates Bi incorporation into GaSb effectively. The highest average Bi content up to 11% with locally up to 13% is achieved, confirmed by Rutherford backscattering spectroscopy and transmission electron microscopy (TEM). X-ray diffraction and TEM show perfect crystal quality for the GaSb1-xBix film with x = 5.6%. The composition dependence room temperature photoluminescence (PL) spectra of the GaSb1-xBix alloys with 0 < x ≤ 13% are reported for the first time. The band-gap energy decreases effectively with increasing the Bi content and in the range of 1 ≤ x ≤ 5.6%, the linear decreasing rate is 37 meV/Bi%. For the highest Bi content GaSb1-xBix, the PL peak energy reaches 0.41 eV (3.0 μm), indicating that GaSb1-xBix alloy has potentials in mid-infrared optoelectronic applications.