Low Specific Contact Resistivity to n-Ge and Well-Behaved Ge n+/p Diode Achieved by Implantation and Excimer Laser Annealing

Excimer laser annealing of phosphorus-implanted p-type germanium substrate with various laser energy densities for n + /p junction were investigated. The effects of laser energy density on the redistribution of dopant, surface morphology, and recrystallization of the amorphous Ge induced by ion implantation were characterized. A low specific contact resistivity of $1.61\times 10^{-6}$ $\Omega$$\cdot$cm 2 was achieved from Al/n-Ge ohmic contact, in which phosphorus-implanted Ge was annealed at a laser energy density of 250 mJ/cm 2 , tailoring a small phosphorus diffusion length, high activation level, and low dopant loss. A well-behaved Ge n + /p diode with a rectification ratio up to $1.99\times 10^{5}$ was demonstrated.