Phosphorus atomic layer doping of germanium by the stacking of multipleδ layers

Abstract

In this paper we demonstrate the fabrication of multiple, narrow, and closely spacedδ-doped P layers in Ge. The P profiles are obtained by repeated phosphine adsorption ontoatomically flat Ge(001) surfaces and subsequent thermal incorporation of P intothe lattice. A dual-temperature epitaxial Ge overgrowth separates the layers,minimizing dopant redistribution and guaranteeing an atomically flat starting surfacefor each doping cycle. This technique allows P atomic layer doping in Ge andcan be scaled up to an arbitrary number of doped layers maintaining atomiclevel control of the interface. Low sheet resistivities (280 ) and high carrier densities (2 × 1014 cm − 2, corresponding to 7.4 × 1019 cm − 3) are demonstrated at 4.2 K.