0.2-4.0 THz broadband terahertz detector based on antenna-coupled AlGaN/GaN HEMTs arrayed in a bow-tie pattern

Area of Science:

• Terahertz (THz) technology
• Semiconductor device physics
• Optoelectronics

Background:

• The demand for broadband and high-sensitivity terahertz detectors is increasing.
• Existing detectors face limitations in performance and spectral coverage.
• Antenna-coupled high-electron-mobility transistors (HEMTs) offer a promising platform for THz detection.

Purpose of the Study:

• To design and verify a broadband terahertz detector with enhanced sensitivity and bandwidth.
• To investigate the performance of antenna-coupled AlGaN/GaN HEMTs across a wide frequency range.
• To characterize the detector's response and noise-equivalent power (NEP) at different temperatures.

Main Methods:

• Fabrication of a detector array with eighteen pairs of dipole antennas covering 0.24 to 7.4 THz.
• Integration of antennas with eighteen AlGaN/GaN HEMTs, sharing common source and drain terminals.
• Characterization of the detector's spectral response using incoherent terahertz radiation from a blackbody in a Fourier-transform spectrometer (FTS).
• Sensitivity measurements using coherent terahertz irradiation to determine noise-equivalent power (NEP).

Main Results:

• A continuous spectral response from 0.2 to 2.0 THz at 298 K and 0.2 to 4.0 THz at 77 K was observed.
• Average NEP of approximately 188 pW/Hz at 298 K and 19 pW/Hz at 77 K (0.2–1.1 THz).
• Maximum optical responsivity of 0.56 A/W and minimum NEP of 7.0 pW/Hz at 0.74 THz achieved at 77 K.
• NEP of 1.7 nW/Hz at 2.0 THz (298 K) and 3 nW/Hz at 4.0 THz (77 K) were measured.

Conclusions:

• The developed antenna-coupled AlGaN/GaN HEMT detector demonstrates broadband operation and high sensitivity.
• The detector performance is significantly enhanced at lower temperatures (77 K).
• Future improvements can be achieved by optimizing coupling components, reducing series resistance, and utilizing smaller gate lengths and higher-mobility materials.