STRAIN-STABILIZED HIGHLY CONCENTRATED PSEUDOMORPHIC SI1-XCX LAYERS IN SI

We present evidence that Si1-xCx layers with x almost-equal-to 0.20 can be grown pseudomorphically on a Si(001) substrate despite the large difference of the C and Si lattice constants. Calculations based on density-functional theory and a Keating model predict that embedded layers of certain structures with stoichiometry Sin-1C where n = 5,6,... are considerably more stable than isolated C impurities. The common feature of these structures is that the carbon atoms tend to arrange as third-nearest neighbors. Multilayer structures grown by molecular beam epitaxy strongly suggest that defect-free heterostructures with such high C concentrations can be fabricated.