Operation of resonant-tunnelling diodes (RTDs) beyond tunnel-lifetime limit and THz sources on the basis of the diodes

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We have predicted theoretically in the past, that the operating frequencies of RTDs are limited neither by their tunnel life time () nor by the tunnel relaxation time (rel) and that properly designed RTDs should have negative differential conductance at the frequencies far beyond the limits imposed by both time constants, i.e., the RTD oscillators should be realizable beyond those limits. The experimental demonstration of the theoretical predictions at the frequencies up 12 GHz has been done by us several years ago. In the first phase of the present project, we have already demonstrated the RTD oscillators with ω up to 3.0 and ωrel up to 6.8 at 109 GHz and the highest oscillation frequency was 150 GHz till now. The aim of the second phase of the project is to demonstrate that RTD oscillators can work also at THz frequencies in the regime ωrel >1 and ω>1 and even in the regime ωrel >>1 and ω>>1. Basically, the aim is to learn how to bring the RTDs to oscillations at their highest possible frequency (particularly in the THz range) and how to design the RTDs properly for that. That should also lead us to realization of the THz oscillators with the operating frequency beyond the present state of the art (831 GHz). We are convinced that this goal will be achieved in the second phase of the project. On one hand, the subject of our project is turning around the issue of clarifying the fundamental limitations of RTDs and it is relevant also to other related electronic devices, like, multi-barrier structures, quantum-cascade lasers, single-electron transistors, etc. On the other hand, the subject has a strong application oriented component. As an outcome of our project an enabling key technology for extremely compact THz sources emerges. The THz sources we are investigating could be sub-mm in dimensions and also potentially cheap. Such kind of sources can revolutionize certain types of THz applications. E.g., the technology of such sources would be an enabling technology for compact THz sensors, spectrometers, etc. No comparably compact and simple THz sources exist. That could be important for all the fields, where THz technology might find application: auto-industry, medicine, biotechnology, product quality control, security, military, communication, etc.