Control of surface morphology through variation of growth rate in SiGe/Si(100) epitaxial films: Nucleation of “quantum fortresses”

The surface morphology of Si0.7Ge0.3 films grown at 550 °C by molecular-beam epitaxy is found to be highly controllable through changes in growth rate. A growth rate of 0.9 A/s results in a surface morphology that begins as shallow pyramidal pits, which then become decorated by ordered quadruplets of islands that surround the edges of the pits. This “quantum fortress” structure represents a symmetry with potential application to quantum cellular automata geometries. A higher growth rate of 3 A/s produces similar results. However, when the growth rate is reduced to 0.15 A/s, the surface morphology that develops instead consists of elongated ridges.

[1]  L. B. Freund,et al.  Evolution of coherent islands in Si 12x Ge x /SiÑ001Ö , 1999 .

[2]  J. W. Matthews,et al.  Defects in epitaxial multilayers: II. Dislocation pile-ups, threading dislocations, slip lines and cracks , 1975 .

[3]  Ross,et al.  Transition States Between Pyramids and Domes During Ge/Si Island Growth. , 1999, Science.

[4]  D. J. Robbins,et al.  The characteristics of strain-modulated surface undulations formed upon epitaxial Si1−xGex alloy layers on Si , 1992 .

[5]  Chen,et al.  Morphological Evolution of Strained Films by Cooperative Nucleation. , 1996, Physical review letters.

[6]  Wolfgang Porod,et al.  Practical issues in the realization of quantum-dot cellular automata , 1996 .

[7]  L. Freund,et al.  SiGe Coherent Islanding and Stress Relaxation in the High Mobility Regime , 1997 .

[8]  D. Robbins,et al.  Evolution of surface morphology and strain during SiGe epitaxy , 1992 .

[9]  Masakazu Kobayashi,et al.  STM study of the Ge growth mode on Si(001) substrates , 1994 .

[10]  Savage,et al.  Kinetic pathway in Stranski-Krastanov growth of Ge on Si(001). , 1990, Physical review letters.

[11]  Leonard,et al.  Critical layer thickness for self-assembled InAs islands on GaAs. , 1994, Physical review. B, Condensed matter.

[12]  Tersoff,et al.  Shape transition in growth of strained islands: Spontaneous formation of quantum wires. , 1993, Physical review letters.

[13]  David J. Srolovitz,et al.  ON THE STABILITY OF SURFACES OF STRESSED SOLIDS , 1989 .

[14]  L. B. Freund,et al.  Real-time stress evolution during Si1-xGex Heteroepitaxy: Dislocations, islanding, and segregation , 1997 .

[15]  T. Thundat,et al.  Cuspidal pit formation during the growth of SixGe1−x strained films , 1995 .

[16]  M. Krishnamurthy,et al.  SELF-ASSEMBLY OF QUANTUM-DOT MOLECULES : HETEROGENEOUS NUCLEATION OF SIGE ISLANDS ON SI(100) , 1998 .

[17]  M. Lagally,et al.  Self-organization in growth of quantum dot superlattices. , 1996, Physical review letters.

[18]  Toshiaki Tamamura,et al.  Self-organized growth of strained InGaAs quantum disks , 1994, Nature.

[19]  W. Tiller,et al.  Interface morphology development during stress corrosion cracking: Part I. Via surface diffusion , 1972 .

[20]  Kastner,et al.  Direct observation of subcritical fluctuations during the formation of strained semiconductor islands , 2000, Physical review letters.

[21]  Guyer,et al.  Morphological Stability of Alloy Thin Films. , 1996, Physical review letters.