D. V. Denisov

Super-radiant mode in InAs—monolayer–based Bragg structures

We report direct experimental evidence of the collective super-radiant mode in Bragg structure containing 60 InAs monolayer-based quantum wells (QWs) periodically arranged in GaAs matrix. Time-resolved photoluminescence measurements reveal an appearance of the additional super-radiant mode, originated from coherent collective interaction of QWs. This mode demonstrates a super-linear dependence of the intensity and radiative decay rate on the excitation power. The super-radiant mode is not manifested in the case if only a small number of QWs is excited.

MBE-grown Si: Er light-emitting structures: Effect of epitaxial growth conditions on impurity concentration and photoluminescence

The technology and properties of light-emitting structures based on silicon layers doped by erbium during epitaxial MBE growth are studied. The epitaxial layer forming on substrates prepared from Czochralski-grown silicon becomes doped by oxygen and carbon impurities in the process. This permits simplification of the Si: Er layer doping by luminescence-activating impurities, thus eliminating the need to make a special capillary for introducing them into the growth chamber from the vapor phase. The photoluminescence spectra of all the structures studied at 78 K are dominated by an Er-containing center whose emission line peaks at 1.542 μm. The intensity of this line measured as a function of the substrate and erbium dopant source temperatures over the ranges 400–700°C and 740–800°C, respectively, exhibits maxima. The edge luminescence and the P line observed in the PL spectra are excited predominantly in the substrate. The erbium atom concentration in the epitaxial layers grown at a substrate temperature of 600°C was studied by Rutherford proton backscattering and exhibits an exponential dependence on the erbium source temperature with an activation energy of ∼2.2 eV.

Influence of antimony on the morphology and properties of an array of Ge/Si(100) quantum dots

The morphological features of the quantum-dot formation in the (Ge,Sb)/Si system during molecular-beam epitaxy are studied using reflection high-energy electron diffraction and atomic-force microscopy. It is found that islands obtained by simultaneous sputtering of Ge and Sb have a higher density and are more homogeneous than in the case of sputtering of pure Ge. The regularities in the island formation are discussed in terms of the theory of island formation in systems with lattice mismatch. The field-emission properties of the grown structures are studied using a scanning electron microscope. The reduced brightness of (Ge,Sb)/Si nanostructures is estimated to be B ∼ 105 A/(cm2 sr V), which is an order of magnitude higher than the brightness of Schottky cathodes.

Double pulse doped InGaAs/AlGaAs/GaAs pseudomorphic high-electron-mobility transistor heterostructures

Double pulse doped (δ-doped) InGaAs/AlGaAs/GaAs pseudomorphic high-electron-mobility transistor (HEMT) heterostructures were grown by molecular-beam epitaxy using a multiwafer technological system. The room-temperature electron mobility was determined by the Hall method as 6550 and 6000 cm2/(V s) at sheet electron densities of 3.00 × 1012 and 3.36 × 1012 cm−2, respectively. HEMT heterostructures fabricated in a single process feature high uniformity of structural and electrical characteristics over the entire area of wafers 76.2 mm in diameter and high reproducibility of characteristics from process to process.

Optical properties of InGaAs/InGaAlAs quantum wells for the 1520–1580 nm spectral range

The optical properties of elastically strained semiconductor heterostructures with InGaAs/InGaAlAs quantum wells (QWs), intended for use in the formation of the active region of lasers emitting in the spectral range 1520–1580 nm, are studied. Active regions with varied lattice mismatch between the InGaAs QWs and the InP substrate are fabricated by molecular beam epitaxy. The maximum lattice mismatch for the InGaAs QWs is +2%. The optical properties of the elastically strained InGaAlAs/InGaAs/InP heterostructures are studied by the photoluminescence method in the temperature range from 20 to 140°C at various power densities of the excitation laser. Investigation of the optical properties of InGaAlAs/InGaAs/InP experimental samples confirms the feasibility of using the developed elastically strained heterostructures for the fabrication of active regions for laser diodes with high temperature stability.

Photoluminescence of heterostructures with GaP1 − xNx and GaP1 − x − yNxAsy layers grown on GaP and Si substrates by molecular-beam epitaxy

The structural and optical properties of heterostructures containing GaP1 − xNx ternary and GaP1 − x − yNxAsy quaternary alloy layers are discussed. The heterostructures are grown by molecular-beam epitaxy on GaP and Si substrates. The structures are studied by the high-resolution X-ray diffraction technique and photoluminescence measurements in a wide temperature range from 10 to 300 K. In the low-temperature photoluminescence spectra of the alloys with a low nitrogen fraction (x < 0.007), two clearly resolved narrow lines attributed to the localized states of nitrogen pairs and the phonon replicas of these lines are observed.

Incorporation of InAs nanostructures in a silicon matrix : growth, structure and optical properties

MBE growth and properties of InAs nanoscale islands formed on silicon are reported. Islands capped with Si emit a photoluminescence band in the 1.3 mm region. Upon annealing at increased substrate temperature, extensive interdiffusion leads to the formation of an InAs solid solution in the Si cap layer. Additionally, InAs-enriched regions with extensions of 6n m, exhibiting two kinds of ordering, are observed. The ordering of InAs molecules occurs, respectively, in (101) and (101( ) planes inclined to (110) and (11( 0) planes parallel to the [001] growth direction.

Light-Emitting Si:Er Structures Produced by Molecular-Beam Epitaxy: High-Resolution Photoluminescence Spectroscopy

The photoluminescence spectra of light-emitting structures based on silicon layers doped with erbium in the course of growth by molecular-beam epitaxy at temperatures ranging from 400 to 700°C are studied at 77 K with a resolution of no worse than 1 cm−1. For the layers grown at the temperatures ≤ 500°C, the narrow lines related to erbium are dominant in the spectra. The full width at the half-maximum of these lines is no larger than 9 cm−1. In this case, at least two types of centers involving the Er3+ ions and carbon impurity are observed. For the layers grown at higher temperatures of epitaxial growth, the broader lines (≥40 cm−1) corresponding to the Er3+ ions in the SiOx precipitates are dominant in the spectra. The dependence of the integrated intensity of photoluminescence of the Er-related centers on the temperature of epitaxial growth is represented by a curve with a peak at 500°C.

Study of Multilayer Structures with InAs Nanoobjects in a Silicon Matrix

MBE-grown multilayer structures with InAs quantum dots embedded in a crystalline silicon matrix were studied by high resolution transmission electron microscopy. The properties of the grown structures depend critically on the substrate temperature, growth cycle sequence, and layer thicknesses. It is shown that the silicon matrix can “accommodate” only a limited volume of InAs in the form of coherent clusters about 3 nm in size. With an increasing amount of deposited InAs, large dislocated InAs clusters are formed during Si overgrowth, accumulating excess InAs.

Distinctive features of molecular-beam epitaxial growth of silicon on Si (100) surfaces in the presence of arsenic

The authors of this paper discuss their studies of the influence of background arsenic pressure on the properties of autoepitaxial layers of silicon grown on Si (100) surfaces by molecular-beam epitaxy. In these investigations the following experimental techniques were used: reflection high-energy electron diffraction (RHEED), scanning tunneling microscopy, x-ray photoelectron spectroscopy, and secondary ion mass spectrometry.