Transient photoconductivity of low temperature GaAs grown by molecular beam epitaxy terahertz radar applications

Optoelectronic sampling techniques have been utilized to characterize transient photoconductivity in low temperature (LT) GaAs grown by molecular beam epitaxy (MBE). Metal-semiconductor-metal (MSM) photoconductive devices have been fabricated on LT-GaAs layers grown at a calibrated substrate temperature of 190 C. Results from on-chip photoconductive sampling measurements demonstrate the ability to generate, propagate, and detect photocurrent pulses of approximately 4 ps duration, which is limited by the optoelectronic measurement system. A carrier mobility of 120 cm(exp 2)/V-s has been estimated from these results, which is a factor of 5-10 times larger than alternative materials used for picosecond photoconductivity. This translates to improved sensitivity for emission and detection of terahertz pulses of electromagnetic (EM) radiation.