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High density of crystal defects is formed in Si layers during their growth on the nanostructured surface composed of dense arrays of Ge islands grown on oxidized Si substrates. Although these defect-rich Si layers exhibit intense photoluminescence only at low temperatures, the forward-biased diodes with the Si layers located in the region of the p-i-n+ junction can emit light at room temperature. The difference suggests that the influence of thermal emission of carriers from defect states on the light emission intensity is essentially reduced when the spatial distribution of carrier density is governed by the bias voltage and band bending. The results show that Si layers emitting light in the 1.4–1.7 μm range at room temperature can be prepared by means of growth. [ABSTRACT FROM AUTHOR]

The Ga-N bond extension and compression at the cores of different types of dislocation in hexagonal GaN films grown on Si(111) substrates have been studied by high-resolution transmission electron microscopy. The relative bond extension and compression are about 6 4 and 7 4% respectively around the cores of mixed dislocations and about 9 6 and 12 7% respectively around the cores of pure edge dislocations. The core structure of a pure edge dislocation is an eightfold atom-column ring. [ABSTRACT FROM AUTHOR]

Abstract: We present a method to form semiconductor nanodots on Si substrates by using ultrathin Si oxide technology and the results on their optical properties. We can form ultra-small semiconductor nanodots with the size of ∼5nm and ultra-high density of ∼1012 cm−2 on Si surfaces covered with ultrathin SiO2 films of ∼0.3nm thickness. We focus on photoluminescence and electroluminescence properties of Ge nanodots embedded in Si films. These structures exhibit intense luminescence in the energy region of about 0.8eV. [Copyright &y& Elsevier]

Ge/Si structures grown on oxidized Si surfaces are studied by means of photoluminescence (PL). High-temperature annealing of the structures leads to the increase of their PL intensity by at least one order of magnitude at energies around 0.82 eV. It is suggested that relaxation of strain, existing in our structures due to the Ge/Si lattice mismatch, occurs through the formation of defects such as interstitial clusters in the Si layer capping the layer of Ge islands. These defects in conjunction with oxygen complexes of the rest of the Si oxide film provide the intense PL in the D1 range. [ABSTRACT FROM AUTHOR]

Highly Si-doped cubic GaN films were grown on a Si(001) substrate coated with a 2.5-nm-thick flat 3C–SiC buffer layer. The Si doping concentration ranged from 1×10[sup 19] to 1×10[sup 21] cm[sup -3]. Upon Si doping, the initial nucleations easily coalesced, producing a flat surface with a 4×1 reconstruction and preferential growth in the [110] direction. The density of stacking faults also increased. The substitution of Ga atoms with Si atoms and the increased density of stacking faults help to relieve the compressive stress in GaN caused by the lattice mismatch of the GaN film and the substrate. GaN showed a strong photoluminescence intensity at room temperature. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Examines silicon(001) 2x1 domain conversions induced by sample electric current. Use of microprobe reflection high-energy electron diffraction; Existence of diffusion anisotropy of silicon adatoms; Preservation of the domain terraces.

Si(111) surface topography changes during Si molecular beam epitaxial growth were observed by reflection electron microscope images using microprobe reflection high-energy electron diffraction (RHEED). When RHEED intensity oscillations were observed at low substrate temperature (350 °C), it was found that the shape of atomic steps on the substrate was preserved during the growth and the surface topographies changed repeatedly with the period of the oscillations. When almost no oscillations were observed at higher substrate temperature (500 °C), the shape of the atomic steps changed during the growth. These observations provide direct evidence that RHEED intensity oscillations occur as the result of layer-by-layer two-dimensional nucleation growth. [ABSTRACT FROM AUTHOR]

Oxidation of partially Ga-terminated Si(111) surfaces with clean 7×7 striped areas along atomic step edges was investigated using scanning reflection electron microscopy. Molecular oxygen exposure of 100 L at the substrate temperatures of 410 °C oxidized Ga atoms on the Ga-terminated areas as well as Si atoms on the clean 7×7 areas. The Ga oxides were selectively desorbed over the Si oxides during annealing. This results in the formation of stripe-patterned Si oxides on the surface. After growth of an 8-monolayer Si film and subsequent annealing, Si grooves with a depth of about 1 nm and a width around 200 nm were formed along the step edges by excess Si-assisted thermal desorption of the Si oxides. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Hexagonal GaN films were grown on Si(111) covered with a thin flat SiC buffer layer under both N- and Ga-rich growth conditions. A flat 2.5-nm-thick SiC layer was an effective buffer layer for GaN growth. The growth mode and microstructure of GaN depended strongly on the Ga/N flux ratios. Under N-rich growth conditions, the growth mode was three dimensional; GaN showed statistical roughening of the surface and a characteristic columnar structure. Under Ga-rich conditions, the GaN growth mode was two dimensional; GaN films with a flat surface and an almost stacking-fault-free microstructure were obtained. The two-dimensional growth mode was facilitated by strong wetting between Ga and SiC(111) at the first Ga-layer deposition on SiC. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: Electric field modulation spectroscopy using scanning tunneling microscopy (STM-EFMS) measurements were performed for a Si(111) surface with epitaxially-grown β-FeSi2 islands. STM-EFMS spectra acquired around the indirect energy gap of Si reproduced the photon energy peak position observed in conventional macroscopic EFMS experiments. However, a considerable discrepancy was found in the energy position of the accompanying spectral dip. We examined two possibilities for the cause of this discrepancy. The first interpretation is that the STM-‘EFMS’ spectra may simply reflect the local density of states based on essentially the same principle as that of tunneling spectroscopy. However, this interpretation is ruled out by the facts that almost identical STM-EFMS spectra are obtained also out of the regime of tunneling. The second interpretation is a spectral distortion due to a large electric field steadily built in the sample surface, which is supported experimentally by a spectral shift of the dip energy that is induced by altering the tip-induced band bending. [Copyright &y& Elsevier]