Effect of mesa geometry on leakage current in Ge 1− x Sn x -based p-n junction diodes

Abstract Ge 1− x Sn x is promising for versatile applications integrable on Si ULSI platforms, but suppressing the leakage current remains a critical challenge. This study investigated the effect of device structure optimization. This point is well-discussed for group III–V semiconductor devices but unclarified for Ge 1− x Sn x -based devices. We fabricated various mesa-structure p-Ge 1− x Sn x /n-Ge diodes as a parameter of mesa depth (mesa angle) to investigate the effect of mesa geometry on leakage current. The current density – voltage characteristics demonstrated a significant reduction in reverse current with increasing the mesa depth. Device size and temperature dependence evaluations suggested that increasing mesa depth suppressed surface leakage current and changed the dominant current mechanism from tunneling to generation. TCAD simulations qualitatively demonstrated that increasing the mesa depth relaxed the electric field at the p-n junction interface. Finally, remaining issues were discussed. This study suggests importance of device structure optimization in enhancing the Ge 1− x Sn x -based device performance.