Thickness-dependent substitutional-Sn-concentration in GeSn-on-insuiator by weak-laser-irradiation-enhanced solid-phase crystallization at low-temperature (180°C)

Effects of film-thickness on substitutional Sn concentration in GeSn films on insulator grown by combination of laser irradiation and subsequent thermal annealing are investigated. Here, the laser fluence is chosen as weak, which is below the critical fluence for crystallization of GeSn. It is clarified that for samples irradiated with low fluence, complete crystallization of a-Geo.8Sno.2 films (thickness: 50-200 nm) is achieved by subsequent thermal annealing at 180°C for 5 h without incubation time. The substitutional Sn concentrations increase with decreasing film thickness. As a result, very high substitutional Sn concentration of ~15%, which corresponds to high-substitution fraction of ~75% of total Sn atoms, is achieved for film thickness of 50 nm. This technique will be useful to realize next-generation high performance devices on flexible insulating substrates.