Publications

Atomic-layer doping of SiGe heterostructures for atomic-precision donor devices

Bussmann, Ezra B.; Gamble, John K.; Koepke, Justin K.; Laroche, D.; Huang, S.H.; Chuang, Y.; Li, J.Y.; Liu, C.W.; Swartzentruber, Brian S.; Lilly, M.P.; Carroll, Malcolm; Lu, Tzu-Ming L.

As a first step to porting scanning tunneling microscopy methods of atomic-precision fabrication to a strained-Si/SiGe platform, we demonstrate post-growth P atomic-layer doping of SiGe heterostructures. To preserve the substrate structure and elastic state, we use a T≤800 ° C process to prepare clean Si0.86Ge0.14 surfaces suitable for atomic-precision fabrication. P-saturated atomic-layer doping is incorporated and capped with epitaxial Si under a thermal budget compatible with atomic-precision fabrication. Hall measurements at T=0.3 K show that the doped heterostructure has R□=570±30Ω, yielding an electron density ne=2.1±0.1×1014cm-2 and mobility μe=52±3cm2V-1s-1, similar to saturated atomic-layer doping in pure Si and Ge. The magnitude of μe and the complete absence of Shubnikov-de Haas oscillations in magnetotransport measurements indicate that electrons are overwhelmingly localized in the donor layer, and not within a nearby buried Si well. This conclusion is supported by self-consistent Schrödinger-Poisson calculations that predict electron occupation primarily in the donor layer.