We have studied implant-induced damage, defect annealing, and recrystallization of B, Ga, P, As, and Sb introduced in Ge by ion implantation at high doses, such that dopant chemical concentrations are above the corresponding solubility in Ge, with energies that target about 100-nm junction depths. It is shown that the amount of damage induced in the Ge lattice increases with the mass of the implanted ion, as expected. Implanted B produces local amorphous regions, although crystalline Ge zones are present in the implanted layer. P is a self-amorphizing ion, creating a continuous amorphous layer during implantation. However, a low thermal budget is sufficient to fully regrow the amorphous layer, without evidence of residual extended defects, as evaluated by crosssectional transmission electron microscopy. Conversely, high concentrations of As cause a significant decrease of the regrowth rate of the damaged layer during rapid thermal annealing in the 400-600°C range studied. Finally, high-dose implantation of heavy ions such as Sb induces dramatic morphologic changes in Ge that are not recovered by post-implant rapid thermal annealing.

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We have studied the thermal stability of HfO2 thin layers on germanium and the substrate interface development. HfO2 was deposited on Ge substrates and annealed in O2 or N2 at 500°C (substrate temperature). After O2 anneal, we observed the formation of hafnium germanate, which is stable at 500°C in N2 as opposed to GeO2 that desorbs as GeO. We believe that this hafnium germanate is an oxygen barrier and as such is at the origin of the much thinner interface between HfO2 and germanium as compared to silicon. In addition, results suggest that the HfGeOx is related to the high interface state density frequently reported for germanium metal oxide semiconductor devices.

We have studied doping profiles, activation levels, and defect annealing of P introduced in Ge by ion implantation at different doses and energy, and annealed under various conditions by rapid thermal annealing. Common to all implant energies, ion-implanted P in Ge exhibits a “box profile” at high implant doses, when a sufficiently high thermal budget is applied—similarly to the concentration-dependent diffusion of P introduced in Ge from a high-concentration solid source. Upon proper annealing conditions, the active P concentration is limited to (5–6)×1019at.∕cm3, implying a 50% activation level of the total retained atoms for high-dose implants and 100% for the low-dose implants. A low thermal budget is sufficient to fully regrow the amorphous layer formed by high-dose P implantations, without evidence of residual defects in the regrown germanium layer and at the end of range of the P implant.