(Invited) In-Situ Doped Epitaxial Growth of Highly Dopant-Activated n +-Ge Layers for Reduction of Parasitic Resistance of Ge-nMISFETs

Abstract

An n +-Ge layer with a carrier density of 7 x 1019 cm-3 (physical dopant concentration = 1 x 1020 cm-3) was successfully grown by choosing an appropriate growth condition with a conventional low-pressure CVD technique. We found that a high activation rate of the n-type dopants can be realized at some limited growth pressure range. Ti contacts on the P-doped n +-Ge epi-layers exhibited ohmic properties in contrast to those on P ion-implanted Ge layers of almost the same dopant concentration. Low sheet resistance of 33 Ω/sq and low specific contact resistivity of 1.2 x 10−6 Ωcm2 were obtained for the 65-nm-thick epi-Ge layers as a result of the high activation rate. By applying the n +-Ge layers to Source/Drain region of GeOI-nMISFETs (Lch=60nm) to reduce the parasitic resistances, a high drive current of 300 mA/mm was obtained at Vd=1V, Vg-Vth=1.5V.