Lateral overgrowth of germanium for monolithic integration of germanium-on-insulator on silicon

A technique to locally grow germanium-on-insulator (GOI) structure on silicon (Si) platform is studied. On (001) Si wafer, silicon dioxide (SiO2) is thermally grown and patterned to define growth window for germanium (Ge). Crystalline Ge is grown via selective hetero-epitaxy, using SiO2 as growth mask. Lateral overgrowth of Ge crystal covers SiO2 surface and neighboring Ge crystals coalesce with each other. Therefore, single crystalline Ge sitting on insulator for GOI applications is achieved. Chemical mechanical polishing (CMP) is performed to planarize the GOI surface. Transmission electron microscopy (TEM) analysis, Raman spectroscopy, and time-resolved photoluminescence (TRPL) show high quality crystalline Ge sitting on SiO2. Optical response from metal-semiconductor-metal (MSM) photodetector shows good optical absorption at 850 nm and 1550 nm wavelength. © 2015 Elsevier B.V. All rights reserved

Evolution Of Thermodynamic Potentials In Closed And Open Nanocrystalline Systems: Ge-si:si(001) Islands

An open (closed) system, in which matter is (not) exchanged through surface diffusion, was realized via growth kinetics. Epitaxially grown Si-Ge:Si (001) islands were annealed in different environments affecting the diffusivity of Si adatoms selectively. The evolution of the driving forces for intermixing while approaching the equilibrium was inferred from Synchrotron x-ray measurements of composition and strain. For the open system, intermixing due to the Si inflow from the wetting layer (reservoir) caused a decrease in the Ge content, leading to a lowering of the elastic energy and an increase in the mixing entropy. In contrast, for the closed system, while keeping the average Ge composition constant, atom rearrangement within the islands led to an increase in both elastic and entropic contributions. The Gibbs free energy decreased in both cases, despite the different evolution paths for the composition profiles. © 2008 The American Physical Society.10022Tsao, J., (1993) Materials Fundamentals of Molecular Beam Epitaxy, , Academic Press, New YorkRatke, L., Voorhees, P.W., (2002) Growth and Coarsening: Ostwald Ripening in Material Processing, , Springer, New YorkCostantini, G., (2004) Appl. Phys. Lett., 85, p. 5673. , APPLAB 0003-6951Magalhaes-Paniago, R., (2002) Phys. Rev. B, 66, p. 245312. , PRBMDO 0163-1829 10.1103/PhysRevB.66.245312Shchukin, V.A., (1995) Phys. Rev. Lett., 75, p. 2968. , PRLTAO 0031-9007 10.1103/PhysRevLett.75.2968Medeiros-Ribeiro, G., (1998) Science, 279, p. 353. , SCIEAS 0036-8075 10.1126/science.279.5349.353Ross, F.M., (1998) Phys. Rev. Lett., 80, p. 984. , PRLTAO 0031-9007 10.1103/PhysRevLett.80.984Rastelli, A., (2001) Phys. Rev. Lett., 87, p. 256101. , PRLTAO 0031-9007 10.1103/PhysRevLett.87.256101Malachias, A., (2003) Phys. Rev. Lett., 91, p. 176101. , PRLTAO 0031-9007 10.1103/PhysRevLett.91.176101Katsaros, G., (2005) Phys. Rev. B, 72, p. 195320. , PRBMDO 0163-1829 10.1103/PhysRevB.72.195320Leite, M.S., (2007) Phys. Rev. Lett., 98, p. 165901. , PRLTAO 0031-9007 10.1103/PhysRevLett.98.165901Kelires, P.C., Tersoff, J., (1989) Phys. Rev. Lett., 63, p. 1164. , PRLTAO 0031-9007 10.1103/PhysRevLett.63.1164Medeiros-Ribeiro, G., Stanley Williams, R., (2007) Nano Lett., 7, p. 223. , NALEFD 1530-6984 10.1021/nl062530kTu, Y., Tersoff, J., (2007) Phys. Rev. Lett., 98, p. 096103. , PRLTAO 0031-9007 10.1103/PhysRevLett.98.096103Lang, C., (2005) Phys. Rev. B, 72, p. 155328. , PRBMDO 0163-1829 10.1103/PhysRevB.72.155328Hadjisavvas, G., (2005) Phys. Rev. B, 72, p. 075334. , PRBMDO 0163-1829 10.1103/PhysRevB.72.075334Medhekar, N.V., Hegadekatte, V., Shenoy, V.B., Phys. Rev. Lett., , PRLTAO 0031-9007Kamins, T.I., Medeiros-Ribeiro, G., Ohlberg, D.A.A., Stanley Williams, R., (2003) J. Appl. Phys., 94, p. 4215. , JAPIAU 0021-8979 10.1063/1.1604957Tersoff, J., (2003) Appl. Phys. Lett., 83, p. 353. , APPLAB 0003-6951 10.1063/1.1592304Müller, P., Thomas, O., (2000) Surf. Sci., 465, p. 764. , SUSCAS 0039-6028 10.1016/S0039-6028(00)00691-9Raiteri, P., Miglio, L., (2002) Phys. Rev. B, 66, p. 235408. , PRBMDO 0163-1829 10.1103/PhysRevB.66.235408Kittel, C., Kroemer, H., (1980) Thermal Physics, , W. H. Freeman, San Francisco, 2nd edBernard, J.E., Zunger, A., (1991) Phys. Rev. B, 44, p. 1663. , PRBMDO 0163-1829 10.1103/PhysRevB.44.1663Malachias, A., (2005) Phys. Rev. B, 72, p. 165315. , PRBMDO 0163-1829 10.1103/PhysRevB.72.16531

Structural and optical properties of Si/Ge nanowire heterojunctions

In crystalline, dislocation-free, Si/Ge nanowire (NW) axial heterojunctions grown using the vapor-liquid-solid (VLS) technique, transmission electron microscopy (TEM) photoluminescence (PL) and Raman spectroscopy reveal a SiGe alloy transition layer with preferential chemical composition and strain. In addition to the lattice mismatch, strain due to the difference in Si and Ge thermal expansion is observed. We find, in agreement with theoretical predictions, that the strain can be partially relived by lateral nanowire expansion in the vicinity of the Si/Ge heteroj unction. In addition to the observed nanowire lateral expansion, the lattice mismatched induced strain could be relaxed by other mechanisms including intermixing, formation of structural defects and partial amorphization. The conclusions are supported by analytical TEM measurements. \ua9 The Electrochemical Society.Peer reviewed: YesNRC publication: Ye