High-performance room-temperature terahertz photodetection using 2-dimensional electron gas channel transport

1. Research Background

Owing to its broadband nature, unique spectral fingerprint, safety, and penetration capabilities, terahertz (THz) waveband (0.1 to 10 THz) holds promise for diverse applications, including biomedical effects, nondestructive testing, communications, and aerospace technologies. Among existing THz detectors, cryogenic detectors typically offer high sensitivity and low noise. However, their practical use is limited by the need for bulky low-temperature (liquid nitrogen or helium) equipment and complex operations. To meet wide application demands, developing room-temperature THz detectors with high sensitivity, fast response, and scalability for large-scale arrays is a key goal for researchers.  

2. Research Progress

Despite extensive research being conducted on various strategies for room temperature (RT) THz detection, they struggle with trade-offs between different figures of merit such as sensitivity, response speed, operating frequency range, and scalability for large-scale arrays. A team led by Professor Huizhen Wu at Zhejiang University achieved rapid, high-sensitivity, broadband room-temperature THz detection by introducing a two-dimensional electron gas (2DEG) channel to transport non-equilibrium carriers. They implemented THz detection using PbTe film and CdTe/PbTe heterojunction semiconductors based on the electromagnetically induced potential well effect. At the CdTe/PbTe heterojunction interface, a 2DEG channel with high carrier concentration, low scattering, and high mobility formed spontaneously. The physical detection mechanism and experimental results highlight the advantages of 2DEG channel transport.  Figure 1 illustrates the mechanistic models of the two detectors under THz radiation, showing how non-equilibrium carriers enter different transport paths. Carriers in the 2DEG channel experience less scattering and achieve faster drift velocities.  

The team characterized the response performance of both detectors (Figures 2–4). Thanks to the high carrier concentration and mobility of the 2DEG, non-equilibrium carriers in the channel exhibit lower recombination rates and reduced scattering probabilities compared to PbTe detector. This enables faster and more efficient carrier collection, broadening the THz response range while enhancing sensitivity, responsivity, and response speed.  

3. Future Prospect

Compared to cryogenic detectors, room-temperature THz detectors hold significant potential for practical applications due to their operational simplicity and cost-effectiveness. The strategy of optimizing transport channels to regulate carrier dynamics provides a new paradigm for developing high-performance THz detection technologies. Given that the CdTe/PbTe heterojunction materials in this study can be epitaxially grown on Si/Ge wafers, integrating 2DEG photodetector focal plane arrays with readout integrated circuits using flip-chip bonding technology could pave the way for high-resolution, real-time imaging systems.  

Sources: https://spj.science.org/doi/10.34133/research.0656