Encapsulation of phosphorus via epitaxial silicon growth for the fabrication of a solid state quantum computer

Full text: A promising fabrication process to realise a Si based quantum computer as proposed by Kane involves (i) hydrogen termination of a Si(100) surface, (ii) atomic lithography using a scanning tunnelling microscope tip to desorb single H atoms, (iii) adsorption of phosphine gas molecules at adsorption sites created in step (ii), and (iv) epitaxial overgrowth of this array of single P atoms on the Si surface with an approximately 20 nm thick Si layer. Steps (i) to (iii) have already successfully been demonstrated by our group. Step (iv) involves incorporation of P atoms at Si lattice sites to electrically activate the dopant atoms, followed by subsequent Si epitaxial overgrowth to encapsulate the P atoms. During Si growth, it is necessary to maintain the initial P atom positions with respect to the Si matrix for addressing these atoms with metal gates formed on top of an insulating barrier. Thus, this process step must aim at minimizing P diffusion and surface segregation during growth while maintaining a high structural quality of the epitaxial layer. Results obtained from epitaxial Si overgrowth of high as well as low phosphine dosed Si surfaces will be shown and a promising growth strategy for the fabrication of the Kane quantum computer presented. This work was supported by the Australian Research Council (ARC), the Australian government and by the US National Security Agency (NSA), Advanced Research and Development Activity (ARDA) and the Army Research Office (ARO) under contract number DAAD19-01-1-0653