Intense THz emission in high quality MBE-grown GaAs film with a thin n-doped buffer

Intense terahertz (THz) emission in high quality GaAs film upon ultrafast excitation is demonstrated. Results showed that high quality GaAs grown by molecular beam epitaxy with a thin n-doped buffer can rival existing intense bare semiconductor THz surface emitters. The incorporation of a 0.2 mu m n-GaAs buffer proved effective in enhancing the THz emission of GaAs by 281% and 295% in reflection and transmission THz time-domain excitation geometries, respectively. The GaAs film was of high crystallinity with or without the n-doped buffer layer as confirmed from X-ray diffraction and Raman scattering. The similar crystalline quality of the two samples was further exemplified by their comparable built-in field strength as measured by photoreflectance spectroscopy. The distinguishable difference in GaAs with and without the doped buffer was observed via low temperature photoluminescence (PL) spectroscopy. The GaAs film with the n-doped buffer exhibited intense GaAs PL while the GaAs film without the n-doped buffer exhibited prominent carbon impurity-related PL. THz enhancement was inferred to be due to the decrease in shallow defects in GaAs with n-doped buffer. (c) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement