X-ray diffraction analysis of high quality InAs/GaSb Type II Superlattices grown by MBE

摘要

High resolution X-ray diffraction is used to study InAs/GaSb superlattices structural properties. The SL materials were grown by molecular beam epitaxy on the GaSb substrates. We optimize the shutter sequences and soak time to improve the SL interface and the material quality. The reciprocal space maps show that the materials are almost fully stained. The angle distance between the zeroth order SL peak and the substrate in ω -2θ spectrum is about 10 arcsec. The full-width half-maximum (FWHM) of the zeroth order SL peak is 25 arcsec. Using a four layer model including two InSb interfaces, we simulated the scanning curve and found there is different layer formed in InAs-on-GaSb and GaSb-on-InAs interfaces. The arsenic pressure and the interface structure are optimized to get better material quality for long wavelength SL samples. With optimized growth condition and suitable InSb-like interface structure, high quality SL samples for both mid and long wavelength range are fabricated. The average roughness from AFM on a 2×2 um~2 scan area is less than 1.5 angstrom.