Effect of nitrogen plasma treatment on carrier mobility in polycrystalline Ge thin films

This study investigates the effects of nitrogen plasma treatment on the carrier mobility of solid-phase-crystallized polycrystalline Ge thin films. Hall measurements reveal that optimal plasma treatment at 100 W for 60 s significantly enhances hole mobility while reducing carrier concentration, suggesting effective defect passivation. Raman and electron backscattered diffraction analyses confirm that these electrical improvements occur without notable changes in crystallinity or grain structure. X-ray photoelectron spectroscopy reveals the formation of Ge-N and Ge-O_xN_y bonding states, with optimal nitrogen incorporation occurring at moderate plasma conditions. In contrast, high-power or prolonged treatment leads to surface degradation and increased oxygen incorporation. These findings demonstrate that nitrogen plasma treatment can improve carrier mobility in polycrystalline Ge through controlled chemical passivation, but only within a narrow processing window. The results provide critical insights for optimizing plasma-based surface engineering in polycrystalline semiconductor devices.