Systematic investigation of stripline width and contact metal effects on terahertz photoconductive antenna performance

Abstract We systematically investigated terahertz photoconductive antennas on GaAs incorporating coplanar striplines of varying widths and two types of contact metallizations (AuGe/Ni/Au and standalone Ti). Measurements of the emitted terahertz power show that AuGe contacts yield stronger emission under low-bias conditions, whereas Ti contacts - initially constrained by Schottky barriers - exhibit superior performance at high bias due to barrier lowering. Terahertz time-domain spectroscopy further confirms the expected classical antenna behavior: decreasing the stripline width shifts the resonance frequency to higher values. At the shortest dipole lengths, however, the emitted spectra of the two metallizations diverge, with Ti-metalized antennas exhibiting higher resonance frequencies. These findings demonstrate that the performance of terahertz photoconductive antennas is constrained by the impedance of metallic contacts, providing essential design considerations for next-generation devices intended to operate at higher terahertz frequencies.