Electrical properties of phosphorus-doped polycrystalline germanium formed by solid-phase and metal-induced crystallization

Electrical properties of poly-Ge films achieved by SPC and MIC methods were investigated through XRD and Hall-effect measurements. In particular, dependency of carrier concentration and mobility on phosphorus (P) and its relationship with Ge vacancy defects working as p-type dopants are studied in poly-Ge samples with varying P implant dose. The existence of P atoms in α-Ge affects the grain size of crystallized poly-Ge films, subsequently changing their carrier concentration and mobility. High dose of P atoms in SPC and MIC poly-Ge samples successfully converts the type of poly-Ge from p (hole) to n (electron). As a result, n-type carrier concentrations of ̃10 ¹⁷ in SPC and ̃10¹⁶ in MIC poly-Ge film (highly doped) are obtained, respectively demonstrating highest mobility of ̃35 cm²/V s and ̃30 cm²/V s at 500 °C and 400 °C.