SEBAT-Based Readout for FET THz Detectors With Intrinsic Power-to-Frequency Conversion

TeraHertz (THz) detection with Field-Effect Transistor-based (FET-based) detectors requires low-noise amplification, which typically involves trade-offs in terms of complexity, power, and area, resulting in severe scalability constraints for pixel integration into imaging arrays. The purposeof this paper is to describea novel approach, fromdesign to experimental validation, that enables active device-level amplification of the signal generated by a FET detector and converts it to a frequency suitable for digital processing. This has been done by exploiting a Single- Electron Bipolar Avalanche Transistor (SEBAT) to build a low-noise compact front-end circuit. The FET output is connected to the SEBAT forming a circuit element that here is defined as a TeraHertz Single-Electron Transistor (THzSET). The FET generates a detection current when it senses the THz signal; this current is then injected into the SEBAT, which generates an avalanche current pulse for each single electron, achieving a devicelevel amplification. The avalanche pulse rate is then evaluated from the signal measured at the SEBAT collector, and performing an FFT of the counts-per-second curve over time it is possible to measure the modulated THz signal applied to the device. The obtained Responsivity RF and the Noise Equivalent Power NEP are respectively 4.61Gcps/W and 88nW/root Hz at 330GHz illumination frequency. This is achieved with sub-mu W power consumption and minimal area overhead: indeed, the pixel and the interface have a total area of 0.146mm(2), where the antenna area is 455 x 320 mu m(2) and the SEBAT area is 27 x 22 mu m(2).