Semiconductor materials for optoelectronic THz systems activated by long-wavelength lasers

Semiconductor materials that can be used for manufacturing THz emitters and THz detectors for pulsed optoelectronic terahertz time-domain spectroscopy systems activated by femtosecond lasers of the infrared wavelength range are reviewed. THz emission from unbiased surfaces of various semiconductors has been investigated and analyzed; it was shown that the best emitter is p-type InAs crystal. Optoelectronic THz detectors were manufactured from several semiconducting materials that are meeting the requirements for such devices such as sub-picosecond electron lifetime, high electron mobility, and large dark resistivity. The best results were achieved when using low-temperature-grown GaBiAs epitaxial layers. Characteristics of THz optoelectronic system employing GaBiAs detector (the frequency bandwidth of 5 THz and the dynamical range of 60 dB) were comparable to those systems based on the Ti:sapphire lasers and GaAs photoconducting antennae.