Spectral measurements of picosecond photoconductivity in terahertz detectors made from low temperature grown GaAs and GaInAs

We report on the performance of photoconductive terahertz detectors made from low temperature grown GaAs (LTG GaAs) and Ga0.7In0.3As (LTG GaInAs) in the wavelength range from 620 to 1550 nm. These THz detectors exhibited a significant sub-bandgap photoconductivity due to the electron transitions from the defect band. A simple model evaluating picosecond photoconductivity was proposed to explain the experimental data. By comparing the modeling results with the experimental data, the defect band position was found to be at 0.77 and at 0.4 eV below the conduction band minimum for LTG GaAs and LTG GaInAs, respectively.