Erbium and Germanium Profiles in Si1 – xGe x Layers Grown by Silicon Sublimation-Source Molecular-Beam Epitaxy in GeH4

The Ge and Er depth profiles in Si_{1 – x} Ge _x layers grown on Si(100) substrates by Si sublimation-source molecular-beam epitaxy in GeH₄ were studied by secondary ion mass spectrometry. The results demonstrate that Ge facilitates Er incorporation into the growing Si–Ge layer. The Er dopant profile becomes sharper with increasing Ge content. The Ge profile also has rather sharp boundaries, indicating that there is no Ge surface segregation, which is attributable to the presence of adsorbed hydrogen, acting as a surfactant.     

Terahertz emission at impurity electrical breakdown in Si(Li)

Terahertz electroluminescence caused by impurity-induced breakdown in lithium-doped silicon crystals is studied. The spectrum of the terahertz emission exhibits lines corresponding to intracenter electronic transitions between excited states of the impurity and sublevels of the ground state of the lithium donor. The spectrum also shows a background signal, which, apparently, is a manifestation of the effects due to heating at electric excitation.     

A random telegraph signal in tunneling silicon p–n junctions with GeSi nanoislands

Technical Physics Letters - We have experimentally discovered random telegraph signal generation in tunneling silicon p +–n + junctions with embedded self-assembled GeSi nanoislands. The...     

Special features of the excitation spectra and kinetics of photoluminescence of the Si<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>:Er/Si structures with relaxed heterolayers

Luminescent properties of heteroepitaxial Si_{1 − x} Ge _x :Er/Si structures with relaxed heterolayers are studied. The results of combined studies of the excitation spectra and kinetics of photoluminescence (PL) are used to single out the components providing the largest contribution to the PL signal of the Si_{1 − x} Ge _x :Er/Si structures in the wavelength region of 1.54 μm. It is shown that relaxation of elastic stresses in the Si_{1 − x} Ge _x :Er heterolayer affects only slightly the kinetic characteristics of erbium luminescence and manifests itself in insignificant contribution of the defects and defect-impurity complexes to the luminescent response of the Si_{1 − x} Ge _x :Er/Si structures. In the excitation spectra of the erbium PL, special features related to the possibility of the rare-earth impurity excitation at energies lower than the band gap of the Si_{1 − x} Ge _x solid solution are revealed. It is shown that a peak the width of which depends on the band gap of the solid solution and the extent of its relaxation is observed in the excitation spectra of the erbium-related PL in the Si_{1 − x} Ge _x :Er/Si structures in the wavelength region of 1040–1050 nm. The observed specific features are accounted for by involvement of intermediate levels in the band gap of the Si_{1 − x} Ge _x :Er solid solution in the process of excitation of an Er³⁺ ion.     

Erbium Segregation in Silicon Layers Grown by Molecular-Beam Epitaxy

In the course of molecular-beam epitaxy of Er-doped Si on Si(100) substrates at 450–650°C, the dopant tends to segregate in the surface layer at doping levels from 10¹⁷ to above 10¹⁹ cm^–3. The introduction of oxygen into the growing epilayer—either from the gas phase at an oxygen pressure of 6.7 × 10^–6 Pa or from an SiO₂ layer on the substrate surface—suppresses the surface segregation of Er.     

Polycrystalline silicon films doped with aluminum during deposition

Aluminum-doped polycrystalline silicon films have been grown by molecular-beam deposition at substrate temperatures between 540 and 600 °C. The grain size increases to 1–8 μm with increasing substrate temperature. High Hall mobilities of the carriers were measured, in the range 30–90 cm²/V·s. Pis’ma Zh. Tekh. Fiz. 23, 83–87 (June 12, 1997)     

Effect of parameters of Ge(Si)/Si(001) self-assembled islands on their electroluminescence at room temperature

The electroluminescence (EL) of multilayered p-i-n structures with the self-assembled Ge(Si)/Si(001) islands are investigated. It is found that the structures with islands grown at 600°C have the highest intensity of the electroluminescence signal at room temperature in the wavelength range of 1.3–1.55 μm. The annealing of structures with the Ge(Si) islands leads to an increase in the EL-signal intensity at low temperatures and hampers the temperature stability of this signal, which is related to the additional Si diffusion into islands during annealing. The found considerable increase in the electroluminescence-signal intensity with the thickness of the separating Si layer is associated with a decrease in the elastic stresses in the structure with an increase in this layer’s thickness. The highest EL quantum efficiency in the wavelength range of 1.3–1.55 μm obtained in investigated structures amounted to 0.01% at room temperature.     

Growth of n-Si layers by molecular-beam epitaxy on the substrates heavily doped with boron

Epitaxial n-Si layers doped with phosphorus or erbium have been grown by sublimation molecularbeam epitaxy at 500°C on heavily boron-doped p ⁺-type substrates with resistivity ρ = 0.005 Ω cm. Distribution profiles of the B, Er, and O impurity concentrations in the samples were determined by secondary-ion mass spectrometry. A thermal annealing of the substrate in vacuum at 1300°C for 10 min and growth at a very low substrate temperature made it possible to obtain an extremely abrupt profile for doping impurities at the layer-substrate interface. This method for growth of n-p ⁺ junctions considerably improves their electrical and luminescent characteristics.     

Comparative analysis of photoluminescence and electroluminescence of multilayer structures with self-assembled Ge(Si)/Si(001) island

Comparative studies of the photoluminescence and electroluminescence of multilayer structures with self-assembled Ge(Si)/Si(001) islands are carried out. The luminescence signal from the islands is observable up to room temperature. Annealing of the structures induces a shift of the luminescence peak to shorter wavelengths. The shift is temperature dependent, making possible controllable variations in the spectral position of the luminescence peak of the Ge(Si) islands in the range from 1.3 to 1.55 μm. The enhancement of the temperature quenching of photoluminescence of the islands with increasing annealing temperature is attributed to the decrease in the Ge content in the islands during annealing and, as a result, to a decrease in the depth of the potential well for holes in the islands. The well-pronounced suppression of the temperature quenching of electroluminescence of the Ge(Si) islands in the unannealed structure with increasing pumping current is demonstrated.     

A Substrate Heater for an Ultrahigh Vacuum

A device for the uniform heating of substrates to a temperature of 1450°C for subsequent molecular-beam epitaxy is described.