Integration of Ⅲ-Ⅴ materials on germanium(Ge)substrate,which has been investigated for decades,provides an effective mediation approach for silicon based optoelectronic devices.[1] GaAsBi,as a relative innovative material,also draw much attention because of its large capacity at band-gap engineering and interesting potential as candidates for near-infrared emitters and detectors.[2,3] In this work,we explore the possibility of herteroepitaxy growth of GaAsBi on Ge substrate.GaAsBi single crystal films are grown on Ge substrate by gas source molecular beam epitaxy.Orientation of the substrate is [100] tilted 6°to [111] and pre-growth annealing is carried out to promote the formation of bi-atom step on the surface.Ga pre-deposition process and low temperature growth of the buffer layer at the beginning of growth prevent the formation of anti-phase domain and inter-diffusion of Ge atoms.Positive mismatch of the epi-layer revealed by high-resolution x-ray diffraction indicates the sufficient incorporation of bismuth(Bi)and near infrared room temperature photoluminescence is also detected by Fourier transform infrared(FTIR)spectrometer.Raman spectrum reveals the bonding type of Bi in the lattice as shown in Fig.1.Atom force microscopy and secondary ion mass spectrometer are also utilized to investigate the thin film quality such as the surface morphology and Bi distribution in the film.