Improved performance of Ge n⁺/p diode by combining laser annealing and epitaxial Si passivation

A method to improve Ge n⁺/p junction diode performance by excimer laser annealing (ELA) and epitaxial Si passivation under a low ion implantation dose is demonstrated. The epitaxial Si passivation layer can unpin the Fermi level of the contact of Al/n-Ge to some extent and reduce the contact resistance. In addition, the fabricated Ge n⁺/p junction diode by ELA plus epitaxial Si passivation exhibits a decreased reverse current density and an increased forward current density, resulting in a rectification ratio of about 6.5×10⁶ beyond two orders magnitude larger than that by ELA alone. The reduced specific contact resistivity of metal on n-doped germanium and well-behaved germanium n⁺/p diode are beneficial for the performance improvement of Ge n-MOSFETs and other opto-electronic devices.