Effect of doping with nitrogen on electrical properties and erbium electroluminescence of a-Si:H(Er) films

The effect of nitrogen doping on the electrical and electroluminescence properties of amorphous hydrogenated silicon films doped with erbium has been studied. The parameters of the material, the characteristics of structures on its base, and the efficiency of Er electroluminescence (λ=1.54 μm) are determined by the excess of the nitrogen doping level over the background value depending on the Er concentration. It is shown that effectively luminescing structures can be obtained by reducing the background concentration, with nitrogen doping remaining at the level of ∼10²¹ cm⁻³. A possible mechanism is proposed, accounting for this effect in terms of two possible forms of nitrogen incorporation into an Er-doped a-Si:H structure: with either an Er-N complex or a Na ₄ ⁺ -Si ₃ ⁻ charged defect pair formed. In this case, the electroluminescence efficiency is determined by the number of these pairs. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 35, No. 10, 2001, pp. 1250–1255. Original Russian Text Copyright ? 2001 by Kon’kov, Terukov, Granitsyna.     

Emission sensitization and mechanisms of electron-excitation migration in structures based on III-nitrides doped with rare-earth elements (Eu,Er, Sm)

The effect of doping with Eu, Er, and Sm rare-earth ions on the shape of the luminescence spectrum for heterostructures with GaN/In _x Ga_{1 ? x} N (0.1 < x < 0.4) quantum wells and from p-GaN〈Mg〉/n-GaN and p-AlGaN/n-GaN junctions is investigated. The results of measurements of the electroluminescence of these structures correlate with the previous data on photoluminescence and Mössbauer spectroscopy. It is shown that it is the GaN “yellow” (5000–6000 Å) band that plays the important role in the excitation of intracenter states in the structures with several GaN/InGaN quantum wells doped with Eu and Sm. In this case, Eu is most likely the sensitizer for Sm. Additional introduction of 3d metal (Fe⁵⁷) in p-GaN〈Mg〉/n-GaN:Eu results in the realization of intracenter transitions in Eu³⁺: ⁵ D ₀ → ⁷ F ₁ (6006 Å), ⁵ D ₀ → ⁷ F ₂ (6195 Å), ⁵ D ₀ → ⁷ F ₃ (6627 Å), and ⁵ D ₁ → ⁷ F ₄ (6327 Å) due to the occurrence of new, efficient channels of excitation transfer to intracenter states and in the effect of Fe on the local environment of rare-earth ions including due to the f–d hybridization enhancement.     

Photoresponse of (In,Ga)N-GaN multiple-quantum-well structures in the visible and UVA ranges

Characterization and analysis of photoresponse in p-n diodes with embedded (In,Ga)N-GaN multiple-quantum-well (MQW) structures are reported. Their dependence on the number of wells and In composition are considered. The influence of device structure on electric fields in the active region and on device responsivity has also been studied. Theoretical considerations as well as photocapacitance and photocurrent measurements show that the position of quantum wells (QWs), either in the quasi-neutral region or in the space charge region, is a critical factor in the collection efficiency. Hence, device photoresponse is not proportional to the number of QWs in photovoltaic mode. Present p-MQW-n devices show a promising performance as UVA and visible photodetectors, with detectivities, D/sup */, higher than 1.2/spl times/10/sup 12/ cm/spl middot/Hz/sup 1/2//spl middot/W/sup -1/ and rejection ratios higher than 10/sup 3/.     

A study of the effect of oxygen on the intensity of erbium photoluminescence in amorphous SiO<Subscript>x</Subscript>:(H,Er) films formed by DC magnetron sputtering

The effect of oxygen on the intensity of erbium photoluminescence at λ=1.54 μm in amorphous a-SiO_x:H(Er) films formed by dc magnetron sputtering was studied. The oxygen content in the gaseous phase ranged from 0.1 to 12 mol %, with other parameters of deposition remaining constant. Analysis of an a-Si:(H, Er, O) system showed that the range of homogeneity of amorphous a-SiO_x:H(Er) is retrograde (T=const). The range of homogeneity can be conventionally divided into two portions, each of which should contain either of two differently charged [Er-O] ⁿ⁻ and [Er-O-Si-O] ^m− clusters (m>n). This inference is confirmed experimentally: in the range of oxygen concentrations amounting to 5.5–8 mol % in the plasma, unusual associative processes take place probably directly above the growing film surface; these processes are caused by the appearance of [Er-O-Si-O] ^m− clusters in the plasma and at the surface. It is these processes that account for the intensification of erbium photoluminescence as the oxygen content increases above 5.5 mol %. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 37, No. 7, 2003, pp. 853–859. Original Russian Text Copyright ? 2003 by Undalov, Terukov, Gusev, Kudoyarova.     

Mechanisms of doping and the intensity of emission from intracenter f-f transitions in the doping Eu impurity in structures with InxGa1 ? x N/GaN quantum wells

Effect of doping with europium on the shape of the spectra of emission from structures with quantum wells based on In _x Ga_1−x N/GaN, on the mechanism of doping, and the intensity of emission caused by intracenter f-f transitions in Eu is studied. According to the data of M?ssbauer spectroscopy, the doping Eu impurity can have the charge state of the impurity ion of Eu²⁺ and Eu³⁺ or Eu³⁺ only. In the case where the charge state of the impurity ion is Eu³⁺, emission related to the intracenter transitions ⁵ D ₀−⁷ F ₂ (λ = 6220 ?) is observed. If the impurity ion can be found in the charge states Eu²⁺ and Eu³⁺, the emission related to the intracenter transitions characteristic of both Eu²⁺ and Eu³⁺ is not observed. Original Russian Text ? M.M. Mezdrogina, V.V. Krivolapchuk, V.N. Petrov, Yu.V. Kozhanova, E.Yu. Danilovski, R.V. Kuz’min, 2009, published in Fizika i Tekhnika Poluprovodnikov, 2009, Vol. 43, No. 4, pp. 467–477.     

Effect of the annealing temperature on erbium ion electroluminescence in Si:(Er,O) diodes with (111) substrate orientation

The influence of the temperature of secondary annealing, stimulating the formation of optically and electrically active centers, on the erbium ion electroluminescence (EL) at λ≈1.54 μm in (111) Si:(Er,O) diodes has been studied. The diodes were fabricated by the implantation of 2.0 and 1.6 MeV erbium ions at doses of 3×10¹⁴ cm⁻² and oxygen ions (0.28 and 0.22 MeV, 3×10¹⁵ cm⁻²). At room temperature, the EL intensity in the breakdown mode grows with the annealing temperature increasing from 700 to 950°C. At annealing temperatures of 975–1100°C, no erbium EL is observed in the breakdown mode owing to the formation of microplasmas. The intensity of the injection EL at 80 K decreases with the annealing temperature increasing from 700 to 1100°C. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 35, No. 10, 2001, pp. 1224–1227. Original Russian Text Copyright ? 2001 by Sobolev, Emel’yanov, Nikolaev.     

Effect of electric field in the course of obtaining a-SiO x :H(Er, O) films by dc magnetron sputtering on their composition and photoluminescence intensity of erbium ions

The effect of electric field on the elemental composition and photoluminescence of films of amorphous hydrogenated silicon doped with erbium and oxygen (a-SiO _x :H(Er, O)) in the course of obtaining these films by dc magnetron sputtering is studied. Two series of films were studied in relation to the electric-field strength in the magnetron, the area of the metallic erbium target, and oxygen content in the working chamber. The first series of films was obtained using an electrically insulated substrate holder, and the second series was obtained with a positive potential at the substrate holder with respect to the cathode. It is shown that, although the character of variation in the elemental composition and photoluminescence intensity for erbium Er³⁺ ions differ appreciably in the films of the two series, both of these factors are determined, as a result, by the processes of sputtering oxidation of the Si and Er targets that represent the cathode.     

The effect of erbium and oxygen on the photoluminescence intensity of erbium and the composition of <Emphasis Type="Italic">a</Emphasis>-SiO<Subscript>x</Subscript>:(H,Er, O) films deposited by DC magnetron sputtering

The effect of the oxygen content (\(C_{O_2 } \)) in the gas mixture (20% of SiH₄ + 80% of Ar) + O₂ and the surface area of an erbium target (S_Er) on the composition and Er³⁺ photoluminescence of amorphous a-SiO_x:(H, Er, O) films prepared by dc magnetron sputtering has been investigated. Analysis of the experimental data shows that [Er-O] and [Er-O-Si-O] clusters are formed in the gas plasma due to the competing processes of oxidation and sputtering of Si and Er targets and to the interaction of [Si-O] and [Er-O] clusters with each other and with the oxygen in the gas phase. The discontinuities in the dependences of the contents of erbium-bound oxygen and erbium in a film, and N _O ^Er-O and N_Er = f(\(C_{O_2 } \), S_Er), at \(C_{O_2 } \) ≈ (5–6.5) mol % supports the hypothesis on the existence of different erbium clusters. The necessary conditions for preparing a-SiO_x:(H, Er, O) films with the highest photoluminescence intensity of erbium ions at a wavelength of 1.54 μm are determined.     

Growth and electrical properties of the (Si/Ge)-on-insulator structures formed by ion implantation and subsequent hydrogen-assisted transfer

Systematic features of endotaxial growth of intermediate germanium layers at the bonding interface in the silicon-on-insulator structure consisting of buried SiO₂ layer implanted with Ge⁺ ions are studied in relation to the annealing temperature. On the basis of the results for high-resolution electron microscopy and thermodynamic analysis of the Si/Ge/SiO₂ system it is assumed that the endotaxial growth of the Ge layer occurs via formation of a melt due to enhanced segregation and accumulation of Ge at the Si/SiO₂ interface. Effect of germanium at the bonding interface on the Hall mobility of holes in silicon layers with nanometer-scale thickness is studied. It is found that the structures including the top silicon layer with the thickness 3–20 nm and incorporating germanium feature the hole mobility that exceeds by a factor of 2–3 the hole mobility in corresponding Ge-free silicon-on-insulator structures.     

Study of the transport properties of organic semiconductors based on europium diphthalocyanine and bi-tris-phthalocyanine complexes with <Emphasis Type="Italic">ortho</Emphasis>-bis(oxymethyl)phenyl bridge and based on erbium and europium dinaphthalocyanine complexes

The transport properties of organic semiconductors based on europium diphthalocyanine and bitris-phthalocyanine complexes with ortho-bis(oxymethyl)phenyl bridge and based on europium and erbium dinaphthalocyanine are studied. The temperature dependences of the dc conductivity for all types of the structures under study are obtained; it is shown that all dependences include two activation portions. For high-temperature portions, the activation energies are determined as 0.85 eV for europium diphthalocyanine with the ortho-bis(oxymethyl)phenyl bridge, 1.135 eV for europium bi-tris-phthalocyanine with the orthobis(oxymethyl)phenyl bridge, 0.98 eV for europium dinaphthalocyanine, and 1.18 eV for erbium dinaphthalocyanine. For the low-temperature activation portion, it is shown that lanthanide ions and their bond with a ligand make the dominant contribution to the conductivity of the structures under study.     

Enhancement of the electroluminescence of organic light emitting devices based on Ir(ppy)3 by doping with metallic and magnetic nanoparticles

Magnetic nanoparticles embedded in the active layer of the Organic Light Emitting Diodes (OLEDs) significantly increases the electroluminescence and the charge transport without influencing the transparency of these devices. A brief comparison was done in order to identify which parameter influences these properties, by comparing the CoFe₂O₄ magnetic nanoparticles with CoFe₂ metallic magnetic nanoparticles, the latter one being obtained by thermal reduction in hydrogen of cobalt ferrite nanoparticles. CoFe₂ have shown a better efficiency of the metallic nanoparticles where probably the main advantage is the higher magnetization property instead of the coercive field. Concerning the charge transport across the OLEDs, these nanoparticles reduce the electron injection, acting as filling traps, which directly increases the electroluminescence and the current at the same voltage.     

Reliability of the doping concentration in an ultra-thin body and buried oxide silicon on insulator (SOI) and comparison with a partially depleted SOI

This study compares the reliability of nMOSFETs with low- and high-doped ultra-thin body and buried oxide (UTBB) with fully depleted (FD) and partially depleted (PD) silicon on insulator (SOI). The high-doped devices display lower off-current leakage performance but more degradation in both hot-carrier stress (HCS) and positive bias temperature instability (PBTI) test at both room temperature and elevated temperature compared with the low-doped devices. The PBTI test indicates that the high-doped devices induce high tunneling leakage and that the degradation is highly associated with temperature. The degradation stabilizes with an increase in stress time. The thinner PD-SOI demonstrates low variation at the threshold voltage and low drive current under HCS. The FD-SOI has better drain leakage control than the PD-SOI.     

The effects of the porous buffer layer and doping with dysprosium on internal stresses in the GaInP:Dy/por-GaAs/GaAs(100) heterostructures

Semiconductors - In structures with a porous buffer layer, residual internal stresses caused by a mismatch between the crystal-lattice parameters of the epitaxial GaInP alloy and the GaAs substrate...     

Consideration of spontaneous polarization in the problem of NH-SiC/3C-SiC/NH-SiC heterostructures formed by cubic (3C) and hexagonal (NH) silicon carbide polytypes

The problem of three-layer NH-SiC/3C-SiC/NH-SiC heterostructures was considered within the model previously proposed for describing the heterojunction between NH-SiC/3C-SiC silicon carbide polytypes, taking into account spontaneous polarization of hexagonal regions. The potential in the cubic 3C region was approximated by a model function constructed from physical considerations. Much attention was paid to the study of the effect of spontaneous polarization and the 3C region thickness on energy characteristics of quantum wells formed near heterojunctions. Original Russian Text ? S.Yu. Davydov, A.V. Troshin, 2008, published in Fizika i Tekhnika Poluprovodnikov, 2008, Vol. 42, No. 10, pp. 1211–1217.     

Photosensitivity of the structures on the Cu(In,Ga)(S,Se)<Subscript>2</Subscript> films obtained by thermal treatment in the S and Se vapors

Using the method of simultaneous sulfurization and selenization of intermetallic Cu-In-Ga layers, single-phase thin films of the Cu(In,Ga)(S,Se)₂ (CIGSS) alloys are obtained. On these films, rectifying photosensitive surface-barrier structures In/p-CIGSS are obtained by vacuum thermal evaporation of pure In. The photosensitivity spectra of the originally obtained structures are studied. The effect of the composition of the alloy films and illumination conditions on the photoelectric parameters of new structures In/p-CIGSS is studied. It is concluded that the obtained CIGSS films are promising for fabrication of high-efficiency thin-film photoconverters.     

Crosstalk suppression in mixed-mode ICs by the /spl pi/ technology and the future with an SOC integration platform: particle-beam stand (PBS)

A /spl pi/ technology (particle-enhanced isolation, PEI) is proposed to employ penetrating proton beams on the already manufactured mixed-mode (analog-digital) IC wafers (prior to packaging) for the suppression of undesirable substrate coupling. Results indicated that an improvement of 25-30 dB could be achieved by applying a relatively low-fluence proton bombardment on the isolation-intended region in a metal pads pattern. Hall measurements of the irradiated spots were conducted and the associated physics are elaborated on. Issues relevant to the commercial-scale implementation of this technology are also pointed out and discussed. Finally, a /spl pi/-technology-based post-very large scale integration (VLSI) concept: the "particle-beam stand" (PBS) is promoted, which, especially with its design rules pushed to the front end, can potentially serve as the general system-on-a-chip (SOC) integration platform and end most mixed-mode and RF SOC development difficulties.     

Cover Picture: White Electroluminescence from a Single‐Polymer System with Simultaneous Two‐Color Emission: Polyfluorene as the Blue Host and a 2,1,3‐Benzothiadiazole Derivative as the Orange Dopant (Adv. Funct. Mater. 7/2006)

New single‐polymer electroluminescent systems containing two individual emission species—polyfluorenes as a blue host and 2,1,3‐benzothiadiazole derivative units as an orange dopant on the main chain—have been designed and synthesized by Wang and co‐workers on p. 957. The resulting single polymers are found to have highly efficient white electroluminescence with simultaneous blue and orange emission from the corresponding emitting species. A single‐layer device has been fabricated that has performance characteristics roughly comparable to those of organic white‐light‐emitting diodes with multilayer device structures. New single‐polymer electroluminescent systems containing two individual emission species—polyfluorenes as a blue host and 2,1,3‐benzothiadiazole derivative units as an orange dopant on the main chain—have been designed and synthesized. The resulting single polymers are found to have highly efficient white electroluminescence with simultaneous blue (λ_max = 421 nm/445 nm) and orange emission (λ_max = 564 nm) from the corresponding emitting species. The influence of the photoluminescence (PL) efficiencies of both the blue and orange species on the electroluminescence (EL) efficiencies of white polymer light‐emitting diodes (PLEDs) based on the single‐polymer systems has been investigated. The introduction of the highly efficient 4,7‐bis(4‐(N‐phenyl‐N‐(4‐methylphenyl)amino)phenyl)‐2,1,3‐benzothiadiazole unit to the main chain of polyfluorene provides significant improvement in EL efficiency. For a single‐layer device fabricated in air (indium tin oxide/poly(3,4‐ethylenedioxythiophene): poly(styrene sulfonic acid/polymer/Ca/Al), pure‐white electroluminescence with Commission Internationale de l'Eclairage (CIE) coordinates of (0.35,0.32), maximum brightness of 12 300 cd m^–2, luminance efficiency of 7.30 cd A^–1, and power efficiency of 3.34 lm W^–1 can be obtained. This device is approximately two times more efficient than that utilizing a single polyfluorene containing 1,8‐naphthalimide moieties, and shows remarkable improvement over the corresponding blend systems in terms of efficiency and color stability. Thermal treatment of the single‐layer device before cathode deposition leads to the further improvement of the device performance, with CIE coordinates of (0.35,0.34), turn‐on voltage of 3.5 V, luminance efficiency of 8.99 cd A^–1, power efficiency of 5.75 lm W^–1, external quantum efficiency of 3.8 %, and maximum brightness of 12 680 cd m^–2. This performance is roughly comparable to that of white organic light‐emitting diodes (WOLEDs) with multilayer device structures and complicated fabrication processes.     

Study of the interfaces in resistive switching NiO thin films deposited by both ALD and e-beam coupled with different electrodes (Si, Ni, Pt, W, TiN)

Thin NiO films, included in a metal/resistive oxide/metal (MRM) stack, are receiving great interest, as they exhibit resistive switching when subjected to an external applied field, and can thus be implemented in a resistive random access memory (ReRAM). The electrical switching characteristic is seen to depend on the NiO/metal coupling. Therefore a characterization of the interface between NiO and the electrode is vital to optimize and get insights on the switching phenomena. In this work we deposited NiO thin films by atomic layer deposition (ALD) at 300 °C and electron beam deposition (e-beam) at 40 °C on Si, Ni, Pt, W and TiN substrates and we characterized them with X-ray reflectivity (XRR), grazing incidence X-ray diffraction (GIXRD) and time of flight secondary ion mass spectrometry (ToF-SIMS). Depending on the growth process, we found an influence of the substrate on the NiO film roughness, which exhibits values in the 1.2-6.2 nm range. NiO electron density was 1.35-1.96 e⁻Å⁻³ spread around the nominal value of 1.83 e⁻ Å⁻³ for bulk cubic polycrystalline NiO. X-ray diffraction showed that NiO is polycrystalline in the cubic phase. ToF-SIMS profiles confirm NiO/Metal interface sharpness and the optimal uniformity of NiO layers. Intermixing phenomena are limited or absent and the presence of contaminants, such as C, F, and Cl is very low.