Experimental clarification of orientation dependence of germanium PMOSFETs with Al₂O₃/GeO_x/Ge gate stack

An extensive and complete experimental investigation with a full layout design of the channel direction was carried out for the first time to clarify the orientation dependence of germanium p-channel metal-oxide-semiconductor field-effect transistors (PMOSFETs). By comparison of gate trans-conductance, drive current, and hole mobility, we found that the performance trend with the substrate orientation for Ge PMOSFET is (110) > (111) ～ (100), and the best channel direction is (110)/110. Moreover, the (110) device performance was found to be easily degraded as the channel direction got off from the 110 orientation, while (100) and (111) devices exhibited less channel orientation dependence. This experimental result shows good matching with the simulation reports to give a credible and significant guidance for Ge PMOSFET design.