Effect of thermal annealing on structural properties of GeSn thin films grown by molecular beam epitaxy
Journal article, 2017
GeSn alloy with 7.68% Sn concentration grown by molecular beam epitaxy has been rapidly annealed at different temperatures from 300 degrees C to 800 degrees C. Surface morphology and roughness annealed below or equal to 500 degrees C for 1 min have no obvious changes, while the strain relaxation rate increasing. When the annealing temperature is above or equal to 600 degrees C, significant changes occur in surface morphology and roughness, and Sn precipitation is observed at 700 degrees C. The structural properties are analyzed by reciprocal space mapping in the symmetric (004) and asymmetric (224) planes by high resolution X-ray diffraction. The lateral correlation length and the mosaic spread are extracted for the epi-layer peaks in the asymmetric (224) diffraction. The most suitable annealing temperature to improve both the GeSn lattice quality and relaxation rate is about 500 degrees C.