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For the prototypical SiGe/Si(001) Stranski-Krastanow (SK) growth system, the influence of intermixing caused by the deposition of a Si cap layer at temperatures Tcap between 300°C and 700°C is studied both for the SiGe wetting layer (WL) and the SiGe islands. Systematic growth experiments were carried out with an ultrahigh resolution of down to 0.005 monolayers (ML) of deposited Ge. The properties of the samples were investigated via photoluminescence (PL) spectroscopy, atomic force microscopy (AFM), and transmission electron microscopy. We studied in detail the influence of Tcap in the three main coverage regions of SiGe SK growth, which are (i) the WL build-up regime, (ii) the island nucleation regime, where most of the Ge is supplied via material transfer from the WL, and (iii) the saturation regime, where the WL thickness remains initially stable. At Tcap = 300°C, we found that both the WL and the island are essentially preserved in composition and shape, whereas at 500°C the WL becomes heavily alloyed during capping, and at 700°C the islands also become alloyed. At Tcap = 500°C we found enhanced WL intermixing in the presence of dome-shaped islands, whereas at Tcap = 700°C the WL properties become dominated by the dissolution of pyramid-shaped islands upon capping. At Ge coverages above ≈6 ML, we found an unexpected thickening of the WL, almost independently of Tcap. This finding suggests that the density and the volume of the dome-shaped islands have an upper limit, beyond which excess Ge from the external source again becomes incorporated into the WL. Finally, we compared PL spectra with AFM-based evaluations of the integral island volumes in order to determine in a straightforward manner the average composition of the SiGe islands. [ABSTRACT FROM AUTHOR]

We present rock-salt IV-VI semiconductor quantum dots fabricated by implantation of Pb+, Te+, or Sn+ ions into epitaxial zinc-blende CdTe layers. PbTe and SnTe nanoprecipitates of high structural quality are formed after implantation by thermal annealing due to the immiscibility of dot and matrix materials. For samples implanted only with Pb+, intense continuous-wave photoluminescence peaked at 1.6 μm at 300 K is found. In contrast, for PbTe quantum dots fabricated by coimplantation of Pb+ and Te+, the 300 K emission peak is observed at 2.9 μm, indicating luminescence from much larger dots. [ABSTRACT FROM AUTHOR]

The formation of PbTe quantum dots (QDs) in a crystalline CdTe host matrix is demonstrated by the annealing of a coherent, heteroepitaxial PbTe layer clad between CdTe layers. The resulting QDs have a centrosymmetric shape and they exhibit intense room-temperature mid-infrared photoluminescence due to an electron-hole pair recombination in the narrow-gap PbTe. The intense luminescence approves the high quality of the QD interfaces, between the sixfold coordinated rocksalt structure of PbTe and the fourfold coordinated zincblende structure of CdTe. To gain further insight into the structural interface properties, we compare quantitatively multislice simulations of HRTEM images with first-principles total-energy calculations in the repeated-slab approximation. The most drastic effect occurs at the electrostatically neutral (110) interface, where we find a lateral spatial offset between the two crystal halves due to rebonding across the interface. For the two polar (001) interfaces, significantly different lattice plane spacings are observed, depending on whether the polar CdTe (001) face is cation or anion-terminated. The agreement between the first-principles calculations and the HRTEM data is excellent. [ABSTRACT FROM AUTHOR]

Self-assembled Ge islands were grown on stripe-patterned Si(001) substrates by solid source molecular beam epitaxy. The surface morphology obtained by atomic force microscopy and cross-sectional transmission electron microscopy images shows that the Ge islands are preferentially grown at the sidewalls of pure Si stripes along the [-110] direction at 650°C or along the trenches, whereas most of the Ge islands are formed on the top terrace when the patterned stripes are covered by a strained GeSi buffer layer. Reducing the growth temperature to 600°C results in a nucleation of Ge islands both on the top terrace and at the sidewall of pure Si stripes. A qualitative analysis, based on the growth kinetics, demonstrates that the step structure of the stripes, the external strain field, and the local critical wetting layer thickness for the islands formation contribute to the preferential positioning of Ge islands on the stripes. [ABSTRACT FROM AUTHOR]

Focuses on a study which examined the electroluminescence, photoluminescence and photocurrent of Si/SiGe p-i-n heterostructures. Experimental procedure; Model of the temperature dependence; Conclusion.

Presents information on a study wherein a theory describing x-ray diffuse scattering from misfit dislocations in epitaxial layers was developed. Methods; Results; Discussion.

Focuses on a study which described the kinetics and electrical properties of solid-phase epitaxial regrown (SPEG) layers of antimony-implanted strained silicon-germanium alloys. Materials and procedure; Results of higher-dose implanted ion backscattering measurements; Information on the activation energy of the SPEG process for the alloy; Findings on the SPEG rate in a rapid thermal annealing.

Pure Si(100) and Si1-xGex (x<0.20) layers, epitaxially grown on Si(100) substrates, were implanted at room temperature with Sb+ ions at an energy of 100 keV and a dose of 1013 cm-2, which was found to be below the critical value for amorphization. Spreading resistance profiling and Hall-effect measurements show that a p-type region was formed in the Si1-xGex alloy layers upon annealing at 500 °C, in spite of the fact that the implanted ion (Sb) is a donor. Only higher-temperature anneals transformed the implanted layer into the expected n-type doping. A p-type region was also formed following Xe implantation, indicating that these results can be attributed to the radiation damage without dependence on the electronic structure of the ion. This phenomenon does not exist at all in pure Si. Rutherford backscattering (channeling) measurements show that the amount of defects formed in the Si1-xGex alloy layer during the implantation process increased with the Ge content, in good agreement with Monte Carlo simulations. These results can explain the observation that the level of the p-type doping increased with the Ge content in the alloys. [ABSTRACT FROM AUTHOR]

Examines the size effects in field-effect induced wires imposed upon a high-mobility Si/Si[sub0.6]Ge[sub0.3] heterostructure by magnetotransport. Data on the temperature-dependent magnetoresistance of the wires and reference sample; Expression for the separation between the equipotentials at the Fermi energy.