The ultrathin strained Si0.2 Ge0.8 quantum well channel (∼5 nm) directly grown on Si substrates is demonstrated with low defect density and high hole mobility. The quantum well Si0.2 Ge0.8 channel reveals an ∼3.2 times hole current enhancement and an ∼3 times hole mobility enhancement as compared with the bulk Si channel. The output current-voltage characteristics under the external mechanical strain confirm the compressive strain in the channel. The external compressive strain further enhances the hole mobility in a Si0.2 Ge0.8 channel.
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