We propose to study, develop, fabricate and characterize a novel device able to amplify and generate electromagnetic radiation at THz frequencies made of a field-effect heterostructure transistor (gated or ungated) placed inside a resonator constituted by two mirrors parallel to the channel. The emission of radiation is perpendicular to the channel through the transistor surface. The mechanism at the basis of the amplification of the electromagnetic wave is a quasi-ballistic acceleration of electrons followed by a fast emission of polar optical phonons, the so-called optical phonon transit time resonance (OPTTR). The conditions necessary to achieve the resonance are the absence of interactions at low energies and a very sharp energy threshold for the emission of optical phonons: these two conditions can be satisfied exploiting the special transport properties of nitrides which are much more adapted than standard III-V materials. The active (i.e. amplifying) region is represented by the bidimensional electron gas created by the confining potential inside the quantum well at the AlGaN/GaN heterojunction. The cyclic movement of electrons in the phase space enables the amplification of electromagnetic waves in a restricted frequency range given by the inverse of the transit time in the phase space. For electric fields of reasonable strength (some kV/cm), this frequency lies in the THz range. The main advantages of the proposed device with respect to existing devices are: 1) a wide range of working temperatures which includes also the liquid nitrogen temperature; 2) high values of the maximum amplification coefficient; 3) wide tuning of the generation frequency, which covers most of the THz range and is obtained by sweeping the applied voltage only; 4) absence of a magnetic field, which simplifies considerably the device design; 5) very narrow amplification band, which is useful for realizing the single-mode generation; 6) simple design favourable to integration in circuits.
Luca VARANI (CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE - DELEGATION REGIONALE LANGUEDOC-ROUSSILLON)
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE - DELEGATION REGIONALE LANGUEDOC-ROUSSILLON
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE - DELEGATION REGIONALE COTE D'AZUR
Help of the ANR 380,000 euros
Beginning and duration of the scientific project: - 36 Months