Terahertz emission enhancement in low-temperature-grown GaAs with an n-GaAs buffer in reflection and transmission excitation geometries

The growth of low-temperature-grown GaAs (LTG-GaAs) on semi-insulating GaAs substrate with a 0.2 mu m n-GaAs buffer demonstrated enhanced terahertz (THz) emission in reflection and transmission excitation geometries via time-domain spectroscopy. The transient photocurrent of the sample in reflection and transmission geometries resulting from ultrafast excitation yielded a 215% and 165% increase in the THz emission, respectively, as compared with a sample grown with an undoped GaAs buffer. The LTG-GaAs film with n-GaAs buffer exhibited a significant increase in its built-in field as supported by calculations and photoreflectance experiments. The enhanced THz emission intensity was comparable with bulk p-InAs.