@article{1fb55b38db664a0f9e0a07d25c2a0058,
title = "Electron charging in epitaxial Ge quantum dots on Si(100)",
abstract = "Electron confinement to heteroepitaxial Ge/Si(100) quantum dots encapsulated in a Si matrix was investigated using capacitance-voltage measurements. Optimized growth conditions produced dot ensembles comprised of either huts and pyramids or dome clusters allowing investigation of electron confinement to these distinct dot morphologies. At room temperature, 20-40 nm diameter hut and pyramid clusters confine ∼0.7 electrons, while 60-80 nm diameter dome clusters confine ∼6 electrons. The greater capacity of dome clusters may be attributed to the four distinct conduction band minima that are deeper than the single minimum found for pyramid clusters using a simple band structure model.",
author = "Sutharsan Ketharanathan and Sourabh Sinha and John Shumway and Jeffery Drucker",
note = "Funding Information: This work was supported by the NSF Grant Nos. DMR 0304743 and DMR 0239819. We acknowledge use of facilities within the LeRoy Eyring Center for Solid State Science, the Center for Solid State Electronic Research, and the Ira A. Fulton High Performance Computing Initiative. Table I. Summary of Ge growth parameters. The deposition rate was 3 ML/min for all samples. Sample Growth temperature ( ° C ) Coverage(ML) Ge dot diameter(nm) Dot density ( cm − 2 ) Comments A 550 5.9 20–40 7 × 10 10 Huts and pyramids B 600 6.5 60–70 4 × 10 9 Domes C 600 7.8 60–80 5 × 10 9 Domes FIG. 1. Schematic sample cross section. FIG. 2. C - V plots for sample A and an identical reference sample without the Ge layer. The capacitance step in the curve for sample A represents the additional capacitance due to electrons confined to the Ge hut and pyramid clusters. A conduction band profile for the structure is shown in the inset. FIG. 3. Δ 2 conduction band energy for a 40 nm Ge 0.7 Si 0.3 pyramid. Grayscale mappings of conduction band energy in meV (a) in a plane parallel to the substrate in the Si region immediately above the pyramid apex and (b) in a {100} plane normal to the substrate that contains the pyramid apex. For (b), the Ge conduction band energy is set to “white” to accentuate the variations in the Si and the scale bar indicates the band energy for Si only. (c) Δ 2 energy along a line normal to the substrate passing through the pyramid apex. The 130 meV deep, 10 nm wide (at 10 meV below the continuum) well at the pyramid apex most strongly binds electrons. Its ground state is 38 meV below the continuum. FIG. 4. Δ 2 conduction band energies for a 70 nm Ge 0.6 Si 0.4 truncated pyramid. Grayscale mappings of Δ 2 band energy in meV (a) in the Si plane immediately above the flat top of the truncated pyramid and (b) in a {100} plane normal to the substrate that contains two of the corners of the square at the top of the truncated pyramid. Note the four distinct wells located atop the corners of the truncated pyramid. For (b), the Ge conduction band energy is set to white to accentuate the variations in the Si and the scale bar indicates the band energy for Si only. (c) Δ 2 energy along a line normal to the substrate passing through one of the four corners in the flat top of the structure. Note that the deepest potential wells are at the four corners of the flat top of the dot. Each is 150 meV deep and 15 nm wide (at 10 meV below the continuum). Their ground states are 60 meV below the continuum. ",
year = "2009",
doi = "10.1063/1.3078799",
language = "English (US)",
volume = "105",
journal = "Journal of Applied Physics",
issn = "0021-8979",
publisher = "American Institute of Physics Publising LLC",
number = "4",
}