Terahertz generation by photoconductors made from low-temperature-grown GaAs annealed at moderate temperatures

A terahertz time-domain spectroscopy system based on a femtosecond Yb:KGW laser, photoconductive emitters made using a low-temperature-grown (LTG) GaAs layer annealed at different temperatures, and a photoconductive detector made using a Si-doped GaBiAs epitaxial layer, has been demonstrated. Useful spectral bandwidth of the system, that might be used in spectroscopy experiments, was up to 3 THz and its dynamical range exceeded 50 dB when the LTG GaAs emitter annealed at 420°C was used. It has been concluded that the breakdown field of as-grown layers is much larger than that of annealed layers; this process provides rather large optical-to-THz radiation conversion efficiencies for the emitters made from moderately annealed LTG GaAs.