Supressing Segregation in Highly Doped Silicon Monolayers

Abrupt dopant profiles and low resistivity are highly sought after qualities in the silicon microelectronics industry and, more recently, in the development of an all epitaxial Si:P based quantum computer. Previously, we have shown that increasing the dopant density by growing multiple layers is ultimately limited the formation of P-P dimers due to the segregation of dopants between multi-layers [1]. To suppress this segregation, and thereby creating more abrupt dopant profiles and higher active carrier densities, we investigated the application of thin room temperature grown silicon layers, so-called locking layers. Atom probe tomography and magneto-transport measurements show these locking layers are effective in suppressing segregation but reduce the active carrier density. However, we find that the careful application of a rapid thermal anneal can restore the active carrier density whilst maintaining an abrupt dopant profile. In this way we were able to achieve a fully activated P dosed layer that is confined within ~1nm and has a 3D dopant density of 2.5-3 atm. %, well beyond what was previously achieved for phosphorus dosed delta-layers.

1. J.G. Keizer, S.R. McKibbin, M.Y. Simmons. The Impact of Dopant Segregation on the Maximum Carrier Density in Si:P Multilayers. ACS Nano, 9(7), pp7080-7084 (2015).