Author:

Keywords:

germanium, implantation, crystallization, solid phase epitaxy, XRD, SIMS, MBE, PECVD, phosphorus, amorphous

Abstract:

Germanium has interesting optical properties and high carrier mobilities, which can add functionality to Si CMOS. Doping of Ge can be achieved by introducing dopants during deposition (co-deposition) or by implantation after deposition. The disadvantage of implantation is the introduction of structural defects. To circumvent the introduction of structural defects during implantation of dopants, we have fabricated amorphous Ge (a-Ge) layers on Si. After implantation, the a-Ge layers were annealed to achieve solid phase epitaxy (SPE). As comparison, we have manufactured epitaxial Ge layers and introduced dopants by implantation and recrystallization. Further on we have fabricated a-Ge layers with co-doping of phosphorus, and crystallized this layer by SPE. XRD has been performed for structural analysis. SIMS is used to analyze the doping profile and diffusion of P. Hall effect is used to assess the resistivity, carrier concentration and mobility. Implantation and recrystallization of crystalline Ge shows better electrical results over implantation and activation of P dopants in a-Ge. Our results indicate limited influence of the Ge structure (amorphous or crystalline) on the dopant profile and diffusion after annealing. Furthermore the SPE process of amorphous layers is influenced when P is implanted. For a-Ge layers with P co-doping, SPE gives excellent electrical activation. Finally, the annealing conditions have significant influence on the amorphous layers when implanted.