Desarrollo de sensores de THz para aplicaciones de imagen y seguridad
The spectral range of Terahertz (THz) is located between 0.1 and 10 THz, i.e. between the microwave – millimetre (wireless communications, radar,…) and infrared regions of the electromagnetic spectrum. The most attractive features of THz radiation from the point of view of their application are: (i) the THz radiation penetrates clothing and the majority of materials used in packaging such as paper and plastic (ii) many substances have a "fingerprint" (own characteristic spectrum) in the range of THz (iii) due to its low photon energy (about a million times smaller than the one of X rays) radiation THz is non-ionising and therefore, is not dangerous for humans (iv) techniques as THz time-domain spectroscopy (THz-TDS) and image in THz, and the generation of radiation from THz high power using non-linear effects are superior to conventional techniques and serve to analyze a wide variety of materials. These properties make THz radiation based systems a powerful and promising tool for different types of applications while maintaining reasonable safety for human beings.
The present research project aims to develop semiconductor sensors for applications in very high frequency (millimeter-wave and Terahertz (THz)). The development includes the phases of modeling/design, fabrication and characterization of sensors. The advantages of these sensors are: (i) low cost (ii) response time very fast as compared to pryroelectric detectors and Si bolometers (iii) operation at room temperature and (iv) integration in silicon technology. The operation of these sensors as THz detectors is based on the coupling between the electrons in the channel of a high mobility FET (HEMT/MODFET) and the incoming electromagnetic radiation through the excitation of plasma waves in the channel.
The first part of the project deals with the design of these devices, using a correct description of charge transport in the device (the suitable models and tools need to be used considering the dimensions of the channel) coupled to the resolution of Maxwell equations in a volume large enough, in electrical terms, around the device; this goes beyond the conventional modeling techniques of electronic devices.
We propose the development and characterization of two types of sensors: (i) sensors based on III-V materials with an Asymetric design of the dual grating-gate (ii) sensors based in Si/SiGe MODFETs with two structures, the first one uses a Log periodic antenna tooth and the second one a super-grating.
This project aims to reduce the "THz gap" in two fundamental aspects: improvement of the modelling Physics to also improve the design and fabrication of sensors with a responsivity higher than the one of state of the art devices. In this project we plan to manufacture sensors with superior performance in terms of sensitivity (responsivity) and NEP (noise equivalent power) as compared to existing technologies.