A terahertz photoconductive antenna detector was fabricated using Be-doped InGaAs/InAlAs superlattice material. The performance of the detector was characterized using a 1550 nm fiber femtosecond laser system and a commercial photoconductive antenna emitter. The results demonstrate that incorporating a Si₃N₄ anti-reflection layer enhances the detector's response, increases the power response amplitude by about 7 dB, extends the detection spectral width to 7.3 THz, and achieves a power dynamic range of 86.0 dB.