Broad-band emission from a multiple asymmetric quantum-well light-emitting diode

The authors demonstrate broadband light-emitting diode (LED) emission, with a full-width-at-half-maximum (FWHM) values >100 nm, based on concurrent multiple-state transitions in a single active layer containing two asymmetric quantum wells in the GaAs/AlGaAs material system. This spectral width is much broader (by a factor of 2.5) than that for commercial edge-emitting LEDs in the GaAs/AlGaAs system. The LED device is well suited for broadband source applications in wavelength-multiplexing-based, fibre-optic sensor network systems.<>     

Resistivity calculations for inhomogeneously doped germanium

An analytical expression defining the total mobility ? in germanium as a function of doping and temperature is obtained. Although based on certain empirical relations, the expression for ? is found to be reasonably valid in the useful and normally encountered concentration and temperature ranges. The mobility thus obtained is used to calculate the average conductivity of diffused impurity layers (p type) in germanium for Gaussian and complementary-error-function distributions. Results thus obtained are found to be in good agreement with those obtained by the numerical integration method.     

Rare-earth scandium chromium garnets as active media forsolid-state lasers

Analysis has shown that the presence of Cr³⁺ ions in rare-earth scandium garnets (RESG) crystals enhances the efficiency of laser ion transitions in these crystals. Results are reported of spectral-luminescent and laser investigations of the most efficient laser media presently achieved with these crystals     

Visible emission from ZnO doped with rare-earth ions

We report the results of a cathodoluminescence (CL) and photoluminescence (PL) study of ZnO-bulk single crystals and epilayer thin-film samples grown on a sapphire (0001) substrate and doped by implantation with rare-earth ions (RE³⁺): Pr³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺ (bulk crystals, co-doped with Li), Sm³⁺, Dy³⁺, and Er³⁺ (epilayers). The PL and PL excitation (PLE) spectra of polycrystalline ZnO doped with RE³⁺ ions (Nd³⁺, Dy³⁺, Er³⁺, and Tm³⁺) and codoped with Li⁺, Cl⁻, and N⁻ ions have also been studied.     

High field emission in germanium point-contact diodes

The effects have been examined of small changes of barrier height on the reverse current of high inverse voltage germanium point-contact diodes. The barrier height was varied by changing the ambient gas. The experimental results are given quantitative interpretation by a field emission theory in the region from about 10 volts to about 150 volts, where other effects become important. Examination of some 50 diodes has shown that diodes which draw low reverse currents behave according to this theory.     

A stress tunable gallium doped germanium infrared detector system

A simple partable cryostat system for studying photoconductivity in semiconductors under variable uniaxial stress at liquid helium temperatures is described. It has been used with a Fourier transform spectrometer to determine the spectral response of the photoconductivity of gallium doped germanium between 10 and 140 cm^?1 as a function of stress and electric field. Details are also presented of the variation of breakdown voltage and dynamic resistance as a function of stress under low background conditions.     

Defect-formation processes in silicon doped with manganese and germanium

Deep-level transient spectroscopy has been used to study the effect of Ge atoms on the behavior of Mn in Si. It is shown that Ge atoms introduced into Si during growth manifest no electrical activity, even though their concentration is rather high: 10¹⁶–10¹⁹ cm⁻³. It is established that the presence of Ge atoms in the Si lattice enhances the efficiency of the formation of the deep levels E _c -0.42 eV and E _c -0.54 eV, which are associated with Mn in the Si lattice: the concentration of these deep levels in Si〈Ge, Mn〉 samples is a factor of 3–4 greater than in Si〈Mn〉. It is found that the presence of Ge atoms stabilizes the properties of the Mn levels in Si: They anneal more slowly than in Si〈Mn〉 by a factor of 5–6. It is assumed that the detected effects are associated with the features of the defect structure of Si doped with Ge and Mn. Fiz. Tekh. Poluprovodn. 32, 676–678 (June 1998)     

Self-organization of germanium highly ordered nanoclusters by the deposition of polycrystalline silicon films doped with germanium

Aspects of the formation of self-organized clusters of germanium (Ge) and solid solution of SiGe, first formed in the mode of deposition of subthin polycrystalline silicon films doped with Ge on the nanoscale film of dielectrics were studied by techniques of atomic force microscopy and Raman scattering by optical phonons in germanium clusters. We found that in subthin polycrystalline silicon films (PSF) doped with Ge on the nanoscale films of dielectrics in conditions of PSF film deposition, there appeared correlated spatial distribution of germanium clusters, as well as silicon rich clusters in certain conditions, i.e., clusters of SiGe solid solution, with the modes of their formation. The relationship of the form, size, and density of Ge nanoclusters (NC), with the conditions of their self-organization is considered. The influence of interdiffusion processes on self-organizing of clusters is established, which is significant at high temperatures of the deposition and doping of PSF. It was found that clusters (islands) could occur on the cleavage surface in the form of four types of topographic features in a classical pyramid form, flat-topped pyramids, and domes and sharp spines, depending on the conditions of the deposition of PSF doped with Ge. The systems of highly organized Ge NC, measuring 3.5–40 nm and with a density of 2.7 × 10⁷–3.5 × 10 cm⁻² were obtained. The possibility, in principle, of managing the geometric parameters of self-organizing NC (nanoislands) by selecting the conditions of their self-organization in the mode of deposition of PSF doped with Ge, was shown.     

Electrical characteristics of p type germanium layers doped by ion implantation

Layers of ptype germanium have been produced by bombardment of ntype specimens with 40keV Ga+ or In+ ions. Measurements of Hall mobility and carrier concentration as a function of depth suggest that the degradation of mobility due to the radiation damage produced by the implant is completely removed after anneal. 50% of Ga ions and 10?15% of In ions became electrically active. These percentages were independent of dose over the range measured (1011cm-2 3 × 1013cm-2).     

Growth and characterization of germanium and boron doped silicon epitaxial films

The epitaxial growth and characterization of in-situ germanium and boron (Ge/B) doped Si epitaxial films is described. As indicated by secondary ion mass spectroscopy and spreading resistance measurements, the total and electrically activated B concentrations are essentially identical and independent of Ge incorporation. The B and Ge concentrations are uniformly distributed in these Ge/B doped films. A slight enhancement of Hall mobility is obtained, possibly due to the stress relief induced by Ge counterdoping. Carrier conduction in these films is due to the activated B with an activation energy of 0.04 eV as revealed by conductivity versus temperature measurements. Ge atoms appear to be isoelectronic with Si atoms in these films. A slight degradation of minority carrier diffusion length is observed. Electrical characterization of PN diodes on these Ge/B doped films do not reveal any anomaly. SiO₂ on these Ge/B doped films has similar oxide fixed charge density, interface state density and dielectric breakdown strength compared to silicon dioxide on boron doped epitaxial films. Electron injection reveals a different transport mechanism of the SiO₂ grown on these Ge/B doped films.     

The variation of impurity ionization with doping in heavily doped germanium

Complete ionization of impurity atoms in semiconductors which is the most common engineering assumption is found to breakdown in the heavily doped condition [1]. Here a calculation of the degree of ionization in degenerate germanium for different doping concentrations is presented.     

Far-infrared laser oscillation due to cyclotron emission in p-type germanium

Far-infrared laser oscillation due to cyclotron emission in the light hole band of p-type germanium was observed under crossed electric and magnetic fields. The wavelength is inversely proportional to magnetic fields with a cyclotron mass ofm _c =0.048m _c . Numerical calculations based on Luttinger Hamiltonian show that mixing of wavefunctions between the light and heavy hole bands causes population inversion betweenn=0 andn=1 light-hole Landau levels. It is also shown that non-equidistant energy spacing of light-hole Landau levels is essential to yield net amplification.     

Heat-treated chromium doped rutile used in an L-band travelling-wave maser

The net. gain of n travelling-wave maser operating at 4-2°K in the frequency range 1680-1050 MHK haa been improved by heat treatment of the active material, chromium-doped rutile (Cr-TiO₂). The heat treatments investigated, diffusion doping, quenching, and annealing were performed in a nearly hydrogen-free atmosphere of oxygen at 1200°C. The maximum net gain with a 3dB bandwidth of 6 MHz was 35 dB at 4·2°K and 1800 MHz. The length of the slow-wave structure was 55 mm. The net gain per unit length is the highest hitherto obtained.     

Broad-band reduction of back-scattering from a thin cylinder

A theoretical and experimental study is made on the wide-band minimization of backscattering from a thin cylinder with a purely reactive central loading. It is concluded that relatively wide minimization bandwidths can be achieved by implementing the reactance loading by a coaxial cavity of high characteristic impedance.     

Electron field emission from ZnO self-organized nanostructures and doped ZnO:Ga nanostructured films

Self-organized ZnO nanostructures were grown by thermal decomposition of metalorganic precursors as well as by carbothermal reduction process. Nanostructured undoped and gallium-doped ZnO nanostructured films were deposited by plasma-enhanced chemical vapor deposition from metalorganic compounds. Electron field emission follows Fowler-Nordheim equation. Efficient electron emission was obtained from self-organized nanostructures due to their geometric shape. Enhanced field emission from ZnO:Ga nanostructured films in comparison with undoped ZnO films is obliged to lowering work function at doping by gallium.     

Luminescence of disordered crystals with langasite structure doped with chromium ions

The luminescence, absorption and circular dichroism spectra of langasite family crystals La₃Ga₅-SiO₁₄ and Sr₃Ga₂Ge₄O₁₄ doped with chromium ions (0.1 at %) are studied in the region of 300–1200 nm. It is demonstrated that these spectra contain bands typical of both a Cr³⁺ ion in an octahedral environment (position 1a) and a Cr⁴⁺ ion in a tetrahedral site (position 2d). The intensities of these bands differ considerably.     

First-principles study of the lattice integration of palladium defects in doped germanium and silicon

Time-differential perturbed angular correlations spectroscopy of palladium in doped germanium has identified palladium-vacancy pairing in n-type antimony-doped, p-type gallium-doped and undoped germanium. In contrast, an equivalent study of palladium defects in doped silicon suggests a different scenario for the silicon host. Palladium-vacancy pairing has been proposed in n-type silicon irrespective of the dopant type (phosphorous, arsenic or antimony) but palladium–boron pairing has been speculated to occur in p-type boron-doped silicon. This thus raises the question: why does palladium pair with a dopant atom in p-type silicon, but with a vacancy in p-type germanium? Based on the density functional theory calculations carried out in this work, it is suggested that the size of the dopant and the host material both play a crucial role in determining the type of palladium-defect complex that is formed. The calculations predict a configuration with the palladium atom on a bond-centered interstitial site pairing with a semi-vacancy on either side in gallium-doped and antimony-doped silicon and germanium, respectively. Whereas, a configuration with the palladium atom on a bond-centered interstitial site pairing with the dopant was proposed in boron-doped silicon and germanium. In further support of the argument, in n-type phosphorous-doped materials the calculations predict a configuration with the palladium atom on a bond-centered interstitial site pairing with a semi-vacancy on either side in silicon, but a configuration with the palladium atom on a bond-centered interstitial site pairing with the phosphorous dopant in germanium.     

Determination of gallium concentration in germanium doped using neutron-induced nuclear transmutation from measurements of resistivity in the region of hopping conductivity

Methods for determining the concentration of gallium in germanium doped using nuclear transmutations induced by thermal and epicadmium neutrons from measurements of resistivity in the region of low (liquid-helium) temperatures are considered. In order to evaluate the gallium concentration, it is suggested to use the concentration dependences of hopping resistivity ρ₃ and the resistivity measured at a temperature of 2.5 K.     

Broad-band photoresponse from InAs quantum dots embedded into InGaAs graded well

A broad-band photoresponse is obtained from undoped InAs multiple quantum dots grown by the molecular beam epitaxy (MBE) technique on a (100) GaAs substrate. The quantum dots were embedded in an In/sub x/Ga/sub 1-x/As graded well where the In mole fraction is chosen in the range of 0.3 /spl ges/ x /spl ges/ 0.0. The photoresponse of the reversed biased device, obtained at 80.5 K and using the normal incident configuration, was found to span the spectral range of 3.5 - 9.5 /spl mu/m. While the photoresponse is significantly high under the influence of the reverse bias voltage, the forward bias photoresponse is found to be negligible.