In-Plane shaped GaAS/AlGaAS modulation-doped structures: Physics and applications for THz/SUBTHz sensing

The terahertz (THz) frequency band which lies between those of microwaves (exploited in mobile phones, satellite communications, television) and the infrared, is becoming increasingly important in a large variety of scientific and electronic applications. In particular, breakthroughs are expected in bio-medical imaging (diagnosis of melanomas, drug levels in blood, DNA profiling, detection of bacteria and viruses), ability to detect chemical signatures (airport security, food hygiene, textiles), satellite communications, etc. The widespread adoption and full commercialization of THz electronics awaits the development of compact, low input power, solid state radiation-sources and detectors. In this work we present compact semiconductor diodes which can be used to detect THz/subTHz radiation. The operation of the device relies on shaping its structure asymmetrically in order to induce non-uniform distribution of the electric field inside of it. Moreover, the shape itself resembles the asymmetrical bow-tie antenna and it serves as a coupler of the incident THz radiation. We describe physics of both bulk and two-dimensional bigradient effect and discuss a possibility to use it for a high frequency sensing.