High transconductance 0.1 μm Ge/Si0.4Ge0.6 Schottky-gated p-MODFETs

The fabrication and characterization of self aligned Ge channel p-modulation doped field effect transistors (MODFET) that exhibit superior dc performance are reported. The epitaxial layer structure was grown on a Si substrate using ultra high vacuum chemical vapor deposition (UHV-CVD) and consisted of a single Si_1-xGe_x buffer region, step graded from x = 0 to x = 60%, followed by a thick layer of Si_0.4Ge_0.6, a p-type region doped with boron, a thin Si_0.4Ge_0.6 offset layer, a pure Ge confinement channel, and a 10 nm thick Si_0.4Ge_0.6 cap layer. The 0.1 μm gate length devices exhibited peak extrinsic transconductances as high as 314 mS/mm at room temperature.