Extremely Sharp Phosphorus Turn-Off Slope and Effect of Hydrogen on Phosphorus Surface Segregation in Epitaxially-Grown Relaxed Si0.7Ge0.3 by RTCVD

Si quantum dots formed in a Si/SiGe two-dimensional gas (2DEG) are a promising candidate for the realization of solid-state quantum computation. To achieve effective Schottky gating for charge manipulation in the normal structures, a sharp phosphorus turn-off is required. We investigated phosphorus surface segregation in relaxed Si_0.7Ge_0.3 epitaxially grown by rapid thermal chemical vapor deposition (RTCVD) and report a record sharp turn-off slope of phosphorus of 6 nm/dec. The hydrogen surface coverage, which increases at low temperature, is a key mechanism for such sharp slopes. We demonstrated the sharp phosphorus turn-off enables a high quality inverted 2DEG of high mobiltiy and low electron density.