Formation of Ohmic Contacts to n-GaAs by Solid Phase Epitaxy of Evaporated and Ion Implanted Ge Films

Ge films evaporated on GaAs(100) substrates have been amorphized by ion implantation and recrystallized epitaxially in the solid phase. Ohmic characteristics have been obtained in Ge/n-GaAs heterostructures by implantation of As+ or P+ in Ge and Si+ at the interface. A two-step annealing method was found to be effective to obtain ohmic characteristics. In two-step annealing, the first annealing step at low temperature is for solid phase recrystallization of Ge films; the second step involves rapid high-temperature annealing in order to activate the implanted species. It has also been found that interdiffusion should be minimized in order to obtain good ohmic characteristics.