Photoconductive antennas are of great scientific and industrial value as the key components for generating and detecting terahertz radiation in terahertz time-domain spectrometers. In this paper, Molecular Beam Epitaxy(MBE) is utilized to prepare InGaAs/InAlAs superlattices as light-absorbing materials for 1 550 nm photoconductive antennas. The high growth quality of the materials is verified by Atomic Force Microscopy(AFM), Photoluminescence(PL), and high-resolution X-ray diffraction. The mesa-structured photoconductive antenna with flat sides is obtained by optimizing the preparation conditions. The fabricated photoconductive terahertz transmitting antenna achieves a spectral width of 4.5 THz in a terahertz time-domain spectroscopy system with a dynamic range of 45 dB.