Research objectives and content
In general the present research project will be devoted to the study of the static and dynamic behaviour of resonant tunnelling diodes (RTD). It is divided mainly on two research objective:
1: Analysis of the effect of two dimensional injection on the I-V characteristic of RTD: It appears very clearly that the performance of RTD strongly depends on the carrier injection. However, the theoretical approaches to study these 2D states are quite scarce and the effect of these states on l-V characteristic not deeply understood. The use of J-V characteristics their derivative (first and second order) will allows us to analyse different issues of quantum transport. In this regard, dependence on temperature of the second derivative of the J-V curve appears different if two dimensional transport is involved rather than a simple three dimensional injection.
2: Study of the dynamic behaviour of RTD to develop equivalent circuit models:While experimental investigation RTDs routinely report l-V curves which exhibit a characteristic 'plateaulike' hysteresis behaviour and bistability, there has been an unfinished debate on whether these phenomena are always a result of oscillation induced by the extrinsic circuit or whether the intrinsic nature of the RTD is sometimes responsible. The clarification of this aspect is a key feature to obtain the real ability of these quantum devices to reach terahertz frequencies. It is important to note that the simulation of AC response is more difficult than the static one. However, within the Quantum Monte Carlo simulator (developed in Barcelona) the analysis of time-dependent performance of RTD is as natural as the static one.
Training content (objective, benefit and expected impact)
Objectives: 1.- Introduce Xavier Oriols in the characterisation technique of RTD.
2.- Test the simulation tools developed in Lille and Barcelona from data provided from IEMN laboratories. 3.- Extract conclusions about the role of 2D states in RTD and about its dynamical behaviour. Benefit: 1.- Complete the Ph.D. studies of Xavier Oriols from an experimental point of view. 2.- Start a good link between the IEMN and UAB in view of more long future term research. 3.- Drive UAB research
efforts on RTD, towards an application oriented environment. Expected impact: Quantum devices (in particular RTDs) are a new emerging alternative that will overcome the current limits of CMOS technology. In this regard, it is expected that the present research project will enlighten the role of 2D states on RTD and the physical mechanisms that govern the AC behaviour of these devices. In general, we hope that this work will be useful as a contribution towards increasing the commercial capabilities of RTD.
Links with industry / industrial relevance (22)
The 'quantum devices' group of the Institute d'Electronique et de Microelectronique du Nord (IEMN) has been working on the fabrication and characterisation of RTD during the last decade. During this time, the IEMN has been in collaboration with Thomson CSF (LCR) over the past, and more recently it is working with NTT Laboratories in Japan. NTT is one of the most relevant and dynamic firms on RTD multi-valued logic applications in the world.