Transition Metal Doped InGaAs Photoconductors for THz Detectors

Transition metal doped InGaAs layers constitute a distinctive class of ultrafast photoconductors for THz emission and detection, which are expected to avoid disadvantages of low-temperature (LT) grown fast photoconductors, such as process temperature limitations. Using molecular beam epitaxy (MBE), iron-doped InGaAs:Fe and rhodium-doped InGaAs:Rh layers with doping levels above 1020 cm−3 were produced and investigated as THz detectors in time-domain spectroscopy (TDS). Compared to state-of-the-art detectors based on low-temperature (LT) grown InGaAs/InAlAs, transition metal doped InGaAs facilitates larger THz peak amplitudes and an improved dynamic range. In particular, InGaAs:Rh receivers allow for an improvement in dynamic range of 15 dB over the whole spectral range, resulting in a peak dynamic range of 105 dB. This improvement increases the resolution in non-destructive testing applications of thin films with THz TDS.