Field screening in low-temperature-grown GaAs photoconductive antennas

This paper investigates the nature of the signals obtained in double-pulse-excitation THz-emission experiments performed on terahertz antennas with low-temperature-grown GaAs as photoconductive material. Results of such measurements on devices containing photoconductive gaps with an area below 100 mum(2) have been interpreted in the past as evidence for screening effects by space charge build-up. We argue that this interpretation leads to discrepancies with what is known about charge-carrier dynamics. In analogy to the much-better-studied response of large-area emitters (photoconductors with an active area on the order of a square centimeter), we argue that radiation-field screening must be considered when interpreting the data of small-area emitters.