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

我们在过去的理论预测中，RTD的工作频率既不受隧道寿命（）也不受隧道弛豫时间（rel）的限制，并且正确设计的RTD应该在远远超出这两个时间常数所施加的限制的频率处具有负差分电导，即，RTD振荡器应该在这些限制之外实现。早在几年前，我们就已经在12ghz以上的频率上进行了理论预测的实验验证。在本项目的第一阶段，我们已经在109 GHz下演示了ω高达3.0和ωrel高达6.8的RTD振荡器，到目前为止，最高振荡频率为150 GHz。该项目第二阶段的目的是证明RTD振荡器也可以在ωrel >1和ω>1的太赫兹频率下工作，甚至在ωrel >>1和ω>>1的状态下工作。基本上，我们的目标是学习如何使rtd达到最高频率的振荡（特别是在太赫兹范围内），以及如何为此正确设计rtd。这也将导致我们实现工作频率超过目前技术水平（831 GHz）的太赫兹振荡器。我们相信，这一目标将在项目的第二阶段实现。一方面，我们项目的主题是围绕澄清rtd的基本局限性的问题，它也与其他相关的电子器件相关，如多势垒结构，量子级联激光器，单电子晶体管等。另一方面，该主题具有强大的面向应用程序的组件。作为我们项目的成果，一项实现极紧凑太赫兹源的关键技术出现了。我们正在研究的太赫兹源的尺寸可能在毫米以下，而且可能很便宜。这种类型的源可以彻底改变某些类型的太赫兹应用。例如，这种源的技术将成为紧凑型太赫兹传感器、光谱仪等的使能技术。没有类似的紧凑和简单的太赫兹源存在。这对太赫兹技术可能应用的所有领域都很重要：汽车工业、医药、生物技术、产品质量控制、安全、军事、通信等。

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.