III-V semiconductor materials, including gallium arsenide (GaAs), indium gallium arsenide (InGaAs), and gallium nitride (GaN), play a pivotal role in terahertz (THz) technology due to their superior electronic and optoelectronic properties. These materials exhibit high electron mobility, direct bandgaps, and tunable carrier dynamics, making them ideal for THz generation, detection, and amplification. The THz spectrum, spanning 0.1 to 10 THz, bridges the gap between microwave and infrared frequencies, enabling applications in imaging, spectroscopy, and high-speed wireless communications.

One of the most efficient THz sources based on III-V materials is the resonant tunneling diode (RTD). RTDs leverage quantum mechanical tunneling through double-barrier heterostructures to generate coherent THz waves. GaAs/AlGaAs RTDs have demonstrated oscillation frequencies exceeding 1 THz with output powers in the microwatt range. The negative differential resistance (NDR) characteristic of RTDs allows for compact, tunable, and room-temperature operation, making them suitable for portable THz systems. InGaAs-based RTDs further extend the frequency range due to their lower effective mass and higher peak velocity, enabling higher-frequency operation with improved efficiency.

Plasmonic structures integrated with III-V semiconductors enhance THz wave interaction and confinement, leading to improved generation and detection. Surface plasmon polaritons (SPPs) in doped InGaAs or GaN films can couple with THz waves, enabling subwavelength confinement and enhanced field intensity. This is particularly useful for near-field THz imaging, where spatial resolution below the diffraction limit is achieved. Plasmonic antennas and metamaterials fabricated on III-V substrates can also modulate THz waves dynamically, enabling applications in reconfigurable THz optics and sensing.

Ultrafast carrier dynamics in III-V materials are critical for THz pulse generation and time-domain spectroscopy. Photoconductive antennas (PCAs) made from low-temperature-grown GaAs (LT-GaAs) or InGaAs are widely used for THz emission and detection. When excited by femtosecond laser pulses, these materials exhibit sub-picosecond carrier lifetimes, allowing for broadband THz pulse generation. The high resistivity and short carrier lifetime of LT-GaAs minimize noise and improve signal-to-noise ratios in THz time-domain spectroscopy (THz-TDS). InGaAs-based PCAs, when optimized with appropriate doping and annealing, extend operation to optical communication wavelengths (1.55 µm), enabling fiber-coupled THz systems.

THz quantum cascade lasers (QCLs) based on GaAs/AlGaAs or InGaAs/InAlAs heterostructures provide high-power, coherent THz emission. These devices rely on intersubband transitions in engineered quantum wells, producing stimulated emission in the THz range. GaN-based QCLs, though less mature, offer potential for higher-temperature operation due to their large longitudinal optical (LO) phonon energy, which suppresses non-radiative scattering. Recent advancements in QCL design have achieved continuous-wave operation at frequencies above 4 THz with output powers exceeding 100 mW, suitable for high-resolution spectroscopy and gas sensing.

In THz detection, III-V materials enable both coherent and incoherent methods. Schottky barrier diodes (SBDs) fabricated on GaAs or InGaAs substrates are widely used for heterodyne detection due to their nonlinear current-voltage characteristics and fast response times. Zero-bias detectors based on InGaAs/InAlAs heterostructures offer high sensitivity without requiring external biasing, simplifying system integration. For direct detection, III-V-based bolometers and field-effect transistors (FETs) provide broadband response with high noise-equivalent power (NEP) performance.

Applications of III-V THz devices span multiple fields. In imaging, THz systems utilizing GaAs or InGaAs emitters and detectors enable non-destructive testing for security screening, pharmaceutical inspection, and semiconductor wafer characterization. The sub-millimeter wavelength allows penetration through non-conductive materials while providing resolution superior to microwave imaging. In spectroscopy, III-V-based THz-TDS systems identify molecular fingerprints of gases, explosives, and biomolecules with high specificity. The rotational and vibrational modes of many compounds exhibit unique absorption features in the THz range, enabling label-free chemical analysis.

Wireless communications benefit from III-V THz technology by addressing the demand for higher data rates. THz frequencies offer bandwidths orders of magnitude wider than current microwave systems, enabling terabits-per-second links. GaAs-based RTDs and InGaAs photomixers have been employed in prototype THz communication systems, demonstrating data transmission over short distances with minimal latency. The low atmospheric absorption at specific THz windows (e.g., 0.3–0.6 THz) further supports outdoor wireless links for future 6G networks.

Despite the progress, challenges remain in improving the power output, efficiency, and thermal management of III-V THz devices. Thermal dissipation in high-frequency RTDs and QCLs limits continuous-wave performance, necessitating advanced heat-sinking techniques. Integration with silicon platforms is another area of research, aiming to combine the performance of III-V materials with the scalability of CMOS technology.

The ongoing development of III-V materials for THz applications promises transformative advances in imaging, sensing, and communication systems. With continued optimization of device architectures and growth techniques, III-V semiconductors will remain at the forefront of THz technology, enabling new capabilities across scientific and industrial domains.