Terahertz detection module based on antenna-coupled AlGaN/GaN HEMTs

Abstract

To accommodate variable terahertz application situations, a compact, high-sensitivity and room-temperature terahertz detection module is designed and demonstrated. The detection module with a volume of less than 350 cm³ integrates a quasi-optically coupled terahertz detector, complementary-metal-oxide-semiconductor-based (CMOS-based) voltage amplifier circuit and bias circuit. An antenna-coupled AlGaN/GaN high-electron-mobility transistor (HEMT) are designed to detect terahertz waves by using self-mixing mechanism. The electrical signal from the detector chip is amplified by a voltage amplifier circuit. The amplifier circuit’s voltage gain can be adjusted from 100 to 700 to accommodate different requirements. The bias circuit provides bias voltage to the gate of the detector. Ability to detect both continuous and pulsed terahertz waves by the module is demonstrated. Under a coherent continuous terahertz irradiation from 0.73 to 1.13 THz, an average noise-equivalent power (NEP) of 23.6 pW/ √ Hz, a maximum optical responsivity of 1281 V/W (w/o Gain) and a minimum NEP of 15.3 pW/ √ Hz are achieved. Under a 4.3 THz pulsed radiation from quantum cascade laser (QCL), the module has a peak optical responsivity of 26 V/W (with Gain = 700) and a NEP of 567 nW/ √ Hz. The rise time of the output signal is 1.14 μs and the fall time is 0.78 μs when the module is operated at a maximum amplification gain of 700 and 6 kHz modulation frequency. To further enhance the sensitivity of the detection module, the design of the detector and the noise of the circuit need to be considered.