Abstract
Ge-based alloys have drawn great interest as promising materials for their superior visible to infrared photoelectric performances. In this study, we report the preparation and optical properties of germanium-bismuth (Ge1-xBix) thin films by using molecular beam epitaxy (MBE). GeBi thin films belong to the n-type conductivity semiconductors, which have been rarely reported. With the increasing Bi-doping content from 2 to 22.2%, a series of Ge1-xBix thin film samples were obtained and characterized by X-ray diffraction, scanning electron microscopy, and atomic force microscopy. With the increase of Bi content, the mismatch of lattice constants increases, and the GeBi film shifts from direct energy band-gaps to indirect band-gaps. The moderate increase of Bi content reduces optical reflectance and promotes the transmittance of extinction coefficient in infrared wavelengths. The absorption and transmittance of GeBi films in THz band increase with the increase of Bi contents.
Highlights
In the field of optical communication, the optical wavelength in dense wavelength division multiplexing technology has extended from C-band (1.53–1.56 μm) to L-band (1.56–1.62 μm) at present
It can be seen that characteristic diffraction peaks which can be attributed to GeBi alloys can be found in all the molecular beam epitaxy (MBE) growth samples
X-ray diffraction (XRD) results indicate that GeBi films were successfully prepared by MBE method and their crystalline properties could be manipulated by changing the Bi content in the Ge1 − xBix films
Summary
In the field of optical communication, the optical wavelength in dense wavelength division multiplexing technology has extended from C-band (1.53–1.56 μm) to L-band (1.56–1.62 μm) at present. In 2010, the University of Stuttgart prepared GeSn films with 0.5–3% Sn content using low growth temperatures and pin detectors with 1.2–1.6-μm operating wavelength [7–10]. We report the preparation and optical properties of an n-type GeBi semiconductor thin film with longer cut-off wavelength by using the MBE method.
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