Precise control of island formation using overgrowth technique on cleaved edges of strained multiple quantum wells

We propose an approach to control the position and the size of semiconductor islands formed by the Stranski - Krastanov growth mode. The method is to perform overgrowth on a cleaved edge of strained multiple quantum wells (SMQW), which give periodically modulated strain to the epitaxial layer. Proper choice of the growth conditions results in the formation of islands selectively on one of the constituents of the SMQW. The usefulness of this method was demonstrated by overgrowing Ge islands on the cleaved edges of Si_0.8Ge_0.2/Si SMQW. The Ge islands were selectively formed on the Si layer at 500 °C and on the Si_0.8Ge_0.2 layer at 600 °C. The former reflects the smaller critical thickness of Ge on Si, and the latter is driven by the minimization of strain energy owing to the smaller lattice mismatch between Ge and Si_0.8Ge_0.2.