Investigation of transport through interfacial barriers between metals and semiconductors

Abstract

Electrical spin injection from a ferromagnetic metal source into a semiconductor can only take place through an interfacial barrier (Rashba, Phys. Rev. B 62, R16267 and Phys. Rev. B 68, 241310). This thesis presents a study of electrical transport through what can be roughly described as two different junction systems, ferromagnetic metal / semiconductor junctions and ferromagnetic metal / insulator / semiconductor junctions to assess their potential for incorporation into spintronic devices. Transport was studied as a function of semiconductor material, silicon and gallium arsenide, spin injector source, Fe3O4 and CogoFe10, temperature, insulator material, AlOx and MgO, and thickness and finally as a function of junction size. The systems can be broken down as follows; GaAs / F63O4, Si / Fe3O4, GaAs / AlOx, / Co90Fe10, GaAs / MgO / Co90Fe10, Si / AlOx / Co90Fe10 and Si / MgO / Co90Fe10- The tunnel barrier (insulator) thickness was increased from 0 nm in 1 nm steps. Alost junctions were fabricated on mid n-type substrates but initially mid p-type and high n and p-type were also used.