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Transport of Spins in Semiconductors

Final Activity Report Summary - TRANSPINS (Transport of Spins in Semiconductors)

A basic building block for the performance evaluation of future spintronic devices (i.e. electronic devices based on the spin quantum property of the electron) has been constructed thanks to the implementation in this project of a Monte Carlo device simulator accounting for the electron spin. This kind of simulators draws random numbers in order to reproduce the randomness inherent in the processes affecting individual electrons which, when studied collectively, determine the average behaviour of an electronic device.

We have developed a scheme to describe within the simulator how electrons being injected from a ferromagnetic contact into a semiconductor may see different resistances depending on their spin, resulting in a current with some degree of spin polarization. This effect, similar in its origin to the giant magnetoresistance, is a keystone ingredient for the correct simulation of a novel class of transistors based on the electron spin. We are now in a position to study the time behaviour (i.e. speed) of these transistors, and delineate the causes that ultimately prevent them from being operated at higher frequencies.

We have also proposed a new kind of structure to obtain arrays of mechanically connected quantum wires. The procedure can be trivially modified to construct quantum wires reaching the active region of a double barrier heterostructure (DBH) at an angle, creating a lateral imbalance in the population of incoming electrons. This imbalance is needed in order for DBH-based spin filters--devices that only let electrons with one type of spin to go through--to operate efficiently.