Dopant Redistribution in High-Temperature-Grown Sb-Doped Ge Epitaxial Films

Heavily doped n-type Ge crystals are essential for Ge-based electronics and optical applications. In this report, we describe the mechanism of dopant redistribution via out-diffusion and re-evaporation processes in Sb-doped Ge epitaxial films grown by molecular beam epitaxy (MBE). The temperature-modulated depositions yielded a uniformly distributed and high Sb concentration (10 19 to 10 21 cm –3 ) on highly ordered crystalline Ge films. Here, the deposition temperatures ( T d ) control the transition of amorphous to epitaxial growth, as well as the Sb concentration profiles. A significant difference in the dopant levels is attributed to Sb out-diffusion that correlated with the diffusion parameters, followed by the re-evaporation from the Ge crystal in high-temperature conditions. Meanwhile, the substituted Sb atoms act as donors that form the n-type Ge film. This understanding of dopant behavior in the epitaxially grown Ge film opens a path to achieve well-defined n + -Ge thin films for Ge-based devices with improved electrical properties.