IEEE Electron Device Letters

Record hole mobility at high vertical fields in planar strained germanium on insulator with asymmetric strain

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Long channel asymmetrically strained Ge narrow width p-MOSFETs were fabricated from (100) biaxially strained Ge (strain ∼2.5%) on insulator. Devices with widths of 0.425-15 μm were fabricated with <110> and <100> channel directions. Reducing the mesa width caused mobility to increase for <110> but decrease for <100> channel orientations. The highest mobility was observed for 0.425-μm-wide mesas with <110> channel direction with an enhancement of 45%-50% relative to biaxially strained Ge at Ninv=6× 1012~cm-2 and a record mobility of 955 cm2/Vs at Ninv=1013~cm -2. Mesas up to 2-μm wide were observed to have enhanced mobilities relative to biaxial Ge, suggesting that even relatively wide mesas can be affected by patterning-induced strain relaxation. © 2014 IEEE.