Silicon Field Effect Transistor as the Nonlinear Detector for Terahertz Autocorellators

Area of Science:

• Terahertz (THz) technology
• Semiconductor device physics
• Nonlinear optics

Background:

• Rectifying field-effect transistors (FETs) are crucial for detecting electromagnetic radiation.
• Understanding their response to high-power incident radiation is essential for advanced applications.
• Previous studies often focused on linear responses or required cryogenic conditions.

Purpose of the Study:

• To investigate the nonlinear response of a silicon CMOS field-effect transistor-based THz detector (TeraFET) in a large signal regime.
• To explore the potential of this nonlinear response for characterizing THz pulses and device parameters.
• To demonstrate a method for direct assessment of intrinsic response time and voltage amplitude calibration.

Main Methods:

• Utilizing a broadband bow-tie antenna coupled Si CMOS FET (TeraFET).
• Performing nonlinear autocorrelation measurements using picosecond-scale pulsed THz radiation.
• Biasing the FET in both subthreshold and above-threshold regimes to observe different response characteristics.

Main Results:

• The TeraFET exhibits a super-linear response to incident THz power when biased below its threshold voltage (Vth = 445 mV).
• Above the threshold voltage, the detected signal shows a linear response to THz power.
• A combination of these regimes enables nonlinear autocorrelation measurements with a single device.

Conclusions:

• The super-linear response in the subthreshold regime is a key phenomenon for nonlinear THz detection.
• This approach allows for direct assessment of intrinsic response time and indirect calibration of voltage amplitude.
• The demonstrated method avoids the need for cryogenic cooling, making THz measurements more accessible.