Rh-doped, InGaAs-based Quantum-Photoconductor with Superior Carrier Mobility-Lifetime Trade-off for THz Time-Domain Spectroscopy

Photoconductive antennas (PCAs) are key elements for the implementation of fiber-coupled terahertz (THz) time-domain spectroscopy (TDS) systems as they provide high infrared-to-THz conversion efficiency. However, their performance is fundamentally limited by the trade-off between carrier mobility and lifetime that is inherent to the photoconducitve material. Here, we present for the first time Rh-doped InGaAs-based quantum photoconductors (QPCs), which overcome this limitation by spatially seperating carrier transport and trapping. With this approach, a sub-picosecond carrier lifetime of 0.75 ps is achieved in combination with very high carrier mobility of 3397 cm²/Vs, which represents a 1.7 times increase compared to state-of-the-art Rh-doped bulk InGaAs PCAs. In addition, we demonstrate the application of these Rh-doped QPCs as photoconductive receivers in a fiber-coupled THz TDS system, achieving a THz spectral bandwidth of more than 6 THz and a peak dynamic range of up to 100 dB. These results are already competitive with the performance of state-of-the-art devices and show the great potential of QPCs for the next generation of fiber-coupled THz TDS systems.