Spontaneously Conversion from Film to High Crystalline Quality Stripe during Molecular Beam Epitaxy for High Sn Content GeSn

Two series of Ge(0.8)Sn(0.2) samples were grown on Ge buffered Si substrate by molecular beam epitaxy (MBE) to investigate the influence of growth temperature and film thickness towards the evolution of surface morphology. A novel phenomena was observed that the Ge(0.8)Sn(0.2) film was segregated and relaxed by the formation of GeSn stripes on the film. Under specific growth condition, the stripes can cover nearly the whole surface. XRD, TEM, AFM, PL and TEM results indicated that the stripes are high quality single crystalline GeSn with Sn content around 5%. The formation of GeSn stripes proposes an effective strategy to fabricate high crystalline quality GeSn stripe on Si, where the Ge(0.8)Sn(0.2) film serves as precursor and the segregated Sn works as catalyst droplets. This technique has great potential for future optoelectronic and microelectronic applications.