  All epitaxial GeSn-on-insulator (GeSnOI) heterostructures have been realized
by conventional molecular beam epitaxy of both GeSn and a thin Gd2O3 insulating
layer, on Si(111) substrates. Analysis of the crystal and surface quality by
high-resolution transmission electron microscopy (HRTEM), high-resolution X-ray
diffraction (HRXRD), and atomic force microscopy (AFM) revealed the formation
of a continuous and fully-relaxed single-crystalline GeSn epilayer, however
with a surface roughness of 3.5 nm. Stacking faults and reflection microtwins
were also observed in cross-sectional HRTEM images. From Hall measurement, the
concentration and mobility of holes, introduced by un-intentional p-type doping
of the GeSn epilayers, were estimated to 8x10^16 cm-3 and 176 cm-2V-1s-1,
respectively. In metal-semiconductor-metal (MSM) Schottky diodes, fabricated
with these GeSnOI heterostructures, the dark current was observed to be lower
by a decade, when compared to similar diodes fabricated with GeSn/Ge/Si(001)
heterostructures. The results presented here are encouraging for the
development of these engineered substrates for (opto)electronic applications.
