Magnetically-Doped III-V Semiconductor Nanostructures

EPSRC : Daniel Blight : EP/R513131/1

As the size of silicon transistors and other circuit features is approaching their physical limits, performance growth has begun to lag behind Moore's law with the time between the introduction of new process nodes increasing and the cost-effectiveness of these nodes decreasing. Two key challenges exist relating to this: (i) the increasing heat generated within silicon chips as more transistors and other devices are added and the difficulty in extracting this heat, and (ii) length scales in the devices are reaching the limit at which quantum effects become dominant and lead to a breakdown of the device performance.

As a result there has been much research into alternative technologies that could help to maintain the historical rate of device performance growth. One field that has shown great promise in that area is the field of spintronics, where the spin of electrons is used as another degree of freedom, adding new capabilities to devices. Spin is a quantum mechanical property and charge carriers (e.g. electrons) possess a spin that is defined as either 'up' or 'down'. This property is not the same as the rotating spin of a coin for example which is either clockwise or anti-clockwise, as quantum mechanics allows the electron to carry both 'up' and 'down' at the same time until a measurement is made. This offers the opportunity to utilise this property to perform complex calculation not feasible by current technologies, whilst also enabling the additional storage of information. Importantly, spins can be 'passed' through a material without needing to establish an electrical current. Such spin currents therefore do not generate heat through the effect of resistance (described by Ohm's law) and therefore may offer a solution to the issue of heat generation in devices.

Research into materials which are able to display spin properties and transfer etc. has been the focus of much attention as a result for a number of decades. One important feature of spin is that it interacts with magnetic fields and hence the doping of materials with magnetic dopants (such as manganese) to enhance their properties has been undertaken. This has shown some impressive results at low temperatures, however the effect of heat when at room temperature (or above) typically means these effects are 'lost'.

To overcome this issue, with the aim of generating materials which operate at room temperature, recent work has indicated that in small structures (nanoscale) the effect of physically confining charge carriers in a structure close to their 'wavelength' can enhance interactions such that they may be observed at higher temperatures. However, the task of doping such small structures with magnetic dopant is very challenging. This project will combine the world-leading expertise in Toronto in generating nanowire materials with the development of a new materials doping capability at Manchester that enables single ions (atoms) to be doped into nanostructures. This will provide a new route to addressing this goal of developing materials suitable for realising room-temperature spin-based devices. It will also offer the opportunity to study quantum effects which in the future might offer an alternative technology to traditional semiconductor electronics (e.g. quantum computing).

The placement will provide the opportunity for a PhD student (Daniel Blight) at the University of Manchester to spend an extended period of time at the University of Toronto to develop the protocols for nanomaterials growth, device fabrication, magnetic doping, and characterisation. The placement will form the basis of a much larger collaboration between the groups and Universities involved and be used as a basis for future funding applications, joint PhD studentships and the fluid exchange of researchers between the groups with minimal barriers to accessing world-leading expertise and experimental capabilities.