Terahertz detection and imaging with sensitive InP DHBTs for estimation of plant water status
14 March 2018
In this work, we present experimental studies of THz detection by different HBTs fabricated using InP double HBT technologies. Different devices were investigated: single-finger devices and multi-finger devices formed using equally spaced parallel single-transistor fingers. We have evaluated the room temperature detection performances of the devices in the sub-THz range from 250 GHz up to 650 GHz and analyse in details the physical mechanisms of THz detection. We investigate two different modes of operation. In the first mode (called latter passive), emitter-base junction of HBT rectifies THz radiation but collector-base junction is unbiased. In the second mode (called latter active), collector-base junction is biased, and the HBT not only detects but also amplifies the detected signal. We compare the two modes and discuss their potential differences and advantages. Finally, THz domain is an excellent non-contact probe of water content in biological tissues. We show that HBTs detectors can be used for THz spectroscopy and 2D THz imaging to study the water dynamics of sorghum (a grass species cultivated for its grain) by monitoring the dehydration kinetics of its leaves.
