No abstract

We demonstrate the critical effect of postgrowth annealing temperature on the properties of low-temperature-grown GaAs. By using annealing temperatures substantially below the 500–600 °C commonly reported, GaAs with high resistivity and with carrier lifetimes as short as 100 fs can be routinely obtained. We discuss the optimum, but different, anneal conditions required for terahertz photoconductive emitters and detectors, and illustrate their use in a continuous-wave system.

We report the coherent generation and detection of ultrabroadband terahertz (THz) radiation using low-temperature-grown GaAs photoconductive antennas as both emitters and receivers. THz radiation with frequency components over 15 THz was obtained, the highest reported for a THz time-domain system based on photoconductive antennas. Such a system has a smooth spectral distribution between 0.3 and 7.5 THz, ideal for spectroscopic applications. In addition, sharp spectral features at 8.0 and 8.8 THz were observed, and explained in terms of optical phonon resonances in the photoconductive antennas.