© 1999 IEEE. Low-temperature grown GaAs (LT-GaAs) has been studied as a potential material for microwave-photonic devices such as a terahertz (THz) radiation emitter. Since the preparation of the LT-GaAs generally requires a post annealing process at around 600 °C, these has been limited to be a small number of the applications combined with other materials. In the present work, we study the photoresponse of amorphous (α-) GaAs prepared at between room temperature and 250 °C by femtosecond time-domain reflection pump-probe measurements and photo-induced THz emission measurements.