THz radiation sensors

Abstract

In the paper, issues associated with the development and exploitation of terahertz (THz) radiation detectors are discussed. The paper is written for those readers who desire an analysis of the latest developments in different type of THz radiation sensors (detectors), which play an increasing role in different areas of human activity (e.g., security, biological, drugs and explosions detection, imaging, astronomy applications, etc.). The basic physical phenomena and the recent progress in both direct and heterodyne detectors are discussed. More details concern Schottky barrier diodes, pair braking detectors, hot electron mixers, and field-effect transistor detectors. Also the operational conditions of THz detectors and their upper performance limits are discussed.

Electron relaxation and mobility in the inverted band quantum well CdTe/Hg1-xCdxTe/CdTe

“…Therefore, these structures are of interest for the creation of semiconductor THz detectors based on hot electrons operating under moderate cooling (up to liquid nitrogen temperature) or ambient temperatures. It is known that narrow gap semiconductors are promising materials for direct THz detectors due to high electron mobility, high carrier concentration and low effective masses of electrons [3,43]. In our case, we should expect the electron relaxation time of about 10 -11 s and scattering mean free path of about 50 μm.…”

“…But these detectors also need deep cooling and are characterized by relatively high response time ( 10 -6 s) [2]. Response of existing un-cooled THz detectors in most cases is limited by times   10 ms (except of Schottky barriers and FET-based THz detectors [3]) and their NEP is of the order of 10 -9 -10 -10 W/Hz 1/2 . Heterostructures based on the narrow band-gap semiconductors (like solid solutions of Hg 1-x Cd x Te) hold a high promise to be prospective materials for creation of THz detectors.…”

Sub-THz radiation room temperature sensitivity of long-channel silicon field effect transistors

“…These data of S V and NEP were obtained without any special antennas incorporated (as antennas serve the contact wires). They correspond to parameters of many other un−cooled THz/sub−THz detectors [1,16] but really they are underesti− mated as no special antennas were applied.…”

“…Today, there exist quite a lot of different types of THz/ sub−THz detectors, the most sensitive ones are deeply cooled to cryogenic or sub−K operation temperatures [1]. Their NEP in some spectral THz/sub−THz regions at low background level reaches NEP~10 -16 -10 -19 W/Hz 1/2 .…”

Detection of terahertz and sub-terahertz wave radiation based on hot-carrier effect in narrow-gap Hg1−xCdxTe

“…At present time there exist a large variety of THz radia− tion sensors [1], e.g., utilizing optical readout bi−material based infrared focal plane arrays (FPAs) [2], heterojunc− tion/homojunction interfacial workfunction internal photoemission (HEIWIP/HIWIP) detectors [3], quantum dot detectors [4,5] and nanobolometers [6], cold−electron bolometers [7], plasma wave detection by field effect transistors (FETs) [8,9], different kind of antenna detec− tors [10], Schottky diodes using semiconducting sin− gle−walled nanotubes [11], and carbon nanotube bolo− meters [12].…”