Experimental and theoretical investigation of defects at (1 0 0) Si1−xGex/oxide interfaces

The identification of a nontrigonal Ge dangling bond at SiO2/Si1−xGex/SiO2 heterostructures and its electrical activity are discussed, both from experimental and theoretical points of view. This dangling bond is observed from multifrequency electron-spin resonance experiments performed at 4.2 K, for typical Ge concentrations in the range 0.4 ≤ x ≤ 0.85. The electrical activity of this defect is revealed from capacitance–voltage characteristics measured at 300 and 77 K, and is found to behave like an acceptor defect. First-principles calculations of the electronic properties of this Ge dangling bond indicate that its energy level approaches the valence band edge of the Si1−xGex layer as the Ge content increases, confirming its acceptor-like nature.