Er离子注入的富硅SiO2MOS-LED的可见和红外电致发光特性

通过Er离子和Si离子注入并结合高温退火制备了Er掺杂的富硅SiO2薄膜以及ITO/SiON/富硅SiO2:Er/Si MOS结构电致发光器件.研究了富Si浓度的变化对Er3+离子掺杂的电致发光器件的发光性能和传导特性的影响.发现不同Si含量对Er3+离子的不同能级的电致发光会产生不同作用.在富Si量小于5％的条件下,...     

宽带隙薄膜材料场电子发射研究的背景、现状和问题

介绍了以金刚石为代表的宽带隙薄膜材料场电子发射研究背景和现状,对金刚石、类金刚石（ＤＬＣ）、立方氮化硼（ｃ－ＢＮ）、氮化铝（Ａ１Ｎ）和碳化硅（ＳｉＣ）薄膜场电子发射研究的进展进行了评述,着重介绍了发射性能与薄膜的结构特征、杂质含量和处理方法间的关系,并讨论了研究中存在的问题。     

1.54 μm room temperature emission from Er-doped Si nanocrystals deposited by ECR-PECVD

In this work, silicon nanocrystals (Si-nc) embedded in a silicon-rich silicon oxide (SRSO) matrix doped with Er³⁺ ions for different erbium and silicon concentrations have been deposited by electron-cyclotron resonance plasma-enhanced chemical-vapor-deposition (ECR-PECVD) technique. Their optical properties have been investigated by photoluminescence (PL) and reflectance spectroscopy.Room temperature emission bands centered at ∼1.54 and at 0.75 μm have been obtained for all samples. The most intense emission band at ∼1.54 μm was obtained for samples with concentrations of 0.45% and 39% for erbium and silicon, respectively. Moreover, it has been found that the broad emission band centered at ∼0.75 μm for all samples shows a very strong interference pattern related to the a specific sample structure and a high sample quality.     

Excitation of erbium in the heterogeneous nanocrystalline matrix of amorphous silicon

The erbium photoluminescence decay kinetics at a wavelength of 1.54 μm in amorphous hydrogenated silicon films obtained at high oxygen concentrations in a magnetron gas discharge is investigated. Optically active erbium is found to exist both in the semiconducting matrix of amorphous silicon and in dielectric nanocrystals of erbium silicate, which are formed in this case. The concentration ratio of excited erbium in amorphous silicon and in the nanocrystals is determined, as well as the time of excitation transfer from erbium in amorphous silicon to erbium in the nanocrystals. The mechanism of erbium excitation in this heterogeneous system is considered. The external quantum yield of erbium photoluminescence measured at a wavelength of 1.54 μm and room temperature is found to be 0.3–0.4%.     

Effect of excimer laser annealing on the silicon nanocrystals embedded in silicon-rich silicon nitride film

The investigations of silicon-rich silicon nitride film grown by plasma-enhanced chemical vapor deposition and then annealed by excimer laser have been carried out systematically. The surface roughness and the crystallization of the films have significantly been improved after the excimer laser annealing. The samples demonstrate visible photoluminescence emission under optical excitation at room temperature. It is found that the emission peak energy as well as emission intensity changes with laser annealing conditions, and the relevant mechanism is discussed in detail. Our investigation exhibits the size controllability of silicon nanocrystals embedded in the silicon nitride film, which implies promising applications in optoelectronic devices such as light-emitting diodes and solar cells.     

LPCVD氮化硅薄膜室温高强度可见光发射

在５．０ｅＶ的激光激发下,在室温下ＬＰＣＶＤ氮化硅薄膜可发射高强度可见荧光,其峰位位置分别为２．９７,２．７７,２．５５,２．３２,２．１０和１．９０ｅＶ的六个ＰＬ峰,建立了其可见荧光发射的能隙态模型,并初步讨论了其发光机制．     

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.     

Quantum confinement in amorphous silicon quantum dots embedded in silicon nitride

Amorphous silicon quantum dots (a-Si QDs) were grown in a silicon nitride film by plasma enhanced chemical vapor deposition. Transmission electron micrographs clearly demonstrated that a-Si QDs were formed in the silicon nitride. Photoluminescence and optical absorption energy measurement of a-Si QDs with various sizes revealed that tuning of the photoluminescence emission from 2.0 to 2.76 eV is possible by controlling the size of the a-Si QD. Analysis also showed that the photoluminescence peak energy E was related to the size of the a-Si QD, a (nm) by E(eV) = 1.56+2.40/a(2), which is a clear evidence for the quantum confinement effect in a-Si QDs.     

Effective excitation cross section of erbium in amorphous hydrogenated silicon under optical pumping

The effective excitation cross section of erbium embedded in an amorphous silicon matrix and the total lifetime of erbium ions in the excited state are determined by measuring the photoluminescence rise time of erbium ions under pulsed excitation of erbium-doped amorphous hydrogenated silicon. An analysis of the rate equations describing the excitation and deexcitation of erbium ions in a semiconducting matrix sheds light on the physical meaning of the effective excitation cross section. It is shown that measurement of the effective excitation cross section permits evaluation of the concentration of optically active erbium ions in the amorphous silicon matrix.     

Influence of the ion synthesis and ion doping regimes on the effect of sensitization of erbium emission by silicon nanoclusters in silicon dioxide films

The photoluminescence spectra of erbium centers in SiO₂ films with ion-synthesized silicon nanoclusters under nonresonant excitation were investigated. Erbium was introduced into thermal SiO₂ films by ion implantation. The dependences of photoluminescence intensity on the dose, the order of ion implantation of Si and Er, the annealing temperature, and additional Ar⁺ and P⁺ ion irradiation regimes, i.e., factors determining the influence of radiation damage and doping on sensitization of erbium luminescence by silicon nanoclusters, were determined. It was found that the sensitization effect and its amplification due to doping with phosphorus are most pronounced under the conditions where nanoclusters are amorphous. The quenching of photoluminescence due to radiation damage in this case manifests itself to a lesser extent than for crystalline nanoclusters. The role of various factors in the observed regularities was discussed in the framework of the existing concepts of the mechanisms of light emission and energy exchange in the system of silicon nanoclusters and erbium centers.     

Excitation mechanisms and localization sites of erbium-doped porous silicon

Porous silicon (PS) is doped with erbium by electrochemical anodisation. The penetration of erbium into the PS layer is confirmed by Rutherford backscattering spectroscopy (RBS) and energy dispersive X-ray (EDX) measurements. Efficient green and infrared emissions were observed at room temperature. The investigations are focused on the evolutions versus temperature and pump intensity of the green photoluminescence (PL) corresponding to the ⁴S_3/2 → ⁴I_15/2 transition. It was found that an erbium related level defect can be involved on the excitation and emission processes of erbium. Pump intensity dependent PL studies revealed that for the electrochemical incorporation, most of the Er³⁺ ions are localized inside the Si nanocrystallites and not in stoichiometric SiO₂. The optical cross-section is close to that of erbium in Si nanocrystallites.     

Photoluminescence of porous silicon saturated with tungsten-tellurite glass with rare-earth metal impurities

It has been shown that the presence of silicon nanoparticles in a layer of porous silicon saturated with tungsten-tellurite glass causes an increase in the photoluminescence quantum efficiency of erbium (1530 nm) by an order of magnitude in the case of long-wavelength excitation and an enhancement of the ytterbium photoluminescence (980 nm) by almost 50 times and erbium photoluminescence by 25 times in the case of short-wavelength pumping. This luminescence enhancement is explained by the formation of additional channels of transfer of external excitation by silicon nanocrystallites in porous silicon to impurity ytterbium and erbium ions in tungsten-tellurite glass.     

氮流量在高氢氛围中对富硅氮化硅薄膜材料结构及其发光特性的影响

采用等离子体增强化学气相沉积技术,以N₂掺入到SiH₄和H₂的沉积方式,分别在玻璃和N型单晶硅片(100)衬底上制备富硅氮化硅薄膜。通过紫外-可见光吸收光谱、傅里叶变换红外吸收光谱(FTIR光谱)、拉曼光谱和光致发光谱(PL谱)分别表征掺氮硅薄膜材料的带隙、结构及其发光特性的变化。结果表明：在氢气的氛围中,随着氮气流量的增加,氢原子能够对薄膜缺陷起到抑制作用,并使较低的SiH₄/N₂流量比下呈现富硅态,但却不利于硅团簇的形成。随着氮原子的掺入,Si—N键的含量增大,带隙增大,薄膜内微结构的无序度也增大,薄膜出现了硅与氮缺陷相关的缺陷态发光;随着氮原子进一步增加,出现了带尾态发光,进一步讨论了发光与结构之间的关联。这些结果有助于采用PECVD制备富硅氮化硅对材料发光与结构特性的优化。     

Features of the pulsed treatment of silicon layers implanted with erbium ions

The formation of thin-film solid solutions of erbium in silicon and synthesis of erbium silicides were performed using continuous implantation of silicon with erbium ions followed by pulsed ion-beam treatment. Structural and optical properties of formed Si:Er layers were studied by Rutherford backscattering, transmission electron microscopy, and low-temperature photoluminescence. The dependences of erbium redistribution, the microstructure of Si:Er layers, and their photoluminescence in the near-IR region on the erbium concentration and pulsed treatment conditions were determined.     

非晶碳氮纳米尖端的微结构和发光机理

利用等离子体增强热丝化学气相沉积系统,用CH₄、H₂和N₂为反应气体,在Si衬底上制备了碳氮纳米尖端。用扫描电子显微镜和显微Raman光谱仪对其进行了表征。在室温下测试了它的发光性能,发光谱由中心约为406 nm和506 nm的两条发光带组成。根据Raman散射谱,对其微结构进行了分析。结合非晶碳氮薄膜的结构和发光机理,分析了它的发光性能。     

Slow-light-enhanced upconversion for photovoltaic applications in one-dimensional photonic crystals

We present an approach to realizing enhanced upconversion efficiency in erbium (Er)-doped photonic crystals. Slow-light-mode pumping of the first Er excited state transition can result in enhanced emission from higher-energy levels that may lead to finite subbandgap external quantum efficiency in crystalline silicon solar cells. Using a straightforward electromagnetic model, we calculate potential field enhancements of more than 18× within he slow-light mode of a one-dimensional photonic crystal and discuss design trade-offs and considerations for photovoltaics.     

Erbium excitation in a SiO<Subscript>2</Subscript>: Si-nc matrix under pulsed pumping

The photoluminescence of Er³⁺ ions in a SiO₂ matrix containing silicon nanocrystals 3.5 nm in diameter is studied under resonant and nonresonant pulsed pumping with pulses 5 ns in duration. The effective erbium excitation cross section under pulsed pumping, σ_eff = 8.7 × 10^?17 cm₂, is close to that for nanocrystals. Comparison of the erbium photoluminescence intensity obtained for a SiO₂ matrix with and without nanocrystals made it possible to determine the absolute concentration of optically active nanocrystals capable of exciting erbium ions, the concentration of optically active erbium, and the average number of erbium ions excited by one nanocrystal. The study revealed that excitation transfer from one erbium ion to another is a relatively slow process, which accounts for the low efficiency of erbium ion excitation under pulsed pumping in a SiO₂ matrix containing silicon nanocrystals.     

Graphene: Nanostructure engineering and applications

Single-crystal erbium silicate nanowires have attracted considerable attention because of their high optical gain. In this work, we report the controlled synthesis of silicon-erbium ytterbium silicate core-shell nanowires and fine-tuning the erbium mole fraction in the shell from x = 0:3 to x = 1:0, which corresponds to changing the erbium concentration from 4:8 × 10²¹ to 1:6 × 10²² cm^-3. By controlling and properly optimizing the composition of erbium and ytterbium in the nanowires, we can effectively suppress upconversion photoluminescence while simultaneously enhancing near-infrared emission. The composition-optimized nanowires have very long photoluminescence lifetimes and large emission cross-sections, which contribute to the high optical gain that we observed. We suspended these concentration-optimized nanowires in the air to measure and analyze their propagation loss and optical gain in the near-infrared communication band. Through systematic measurements using wires with different core sizes, we obtained a maximum net gain of 20±8 dB·mm^-1, which occurs at a wavelength of 1534 nm, for a nanowire with a diameter of 600 nm and a silicon core diameter of 300 nm.

     

Erbium photoluminescence excitation spectroscopy in Si: Er epitaxial structures

Excitation spectra of erbium photoluminescence in Si: Er epitaxial structures are studied within a broad pump wavelength range (λ_ex = 780–1500 nm). All the structures studied reveal a fairly strong erbium photoluminescence signal at photon energies substantially smaller than the silicon band-gap width (λ = 1060 nm) with no exciton generation. A possible mechanism of erbium ion excitation in silicon without exciton involvement is discussed.     

Modified Fowler–Nordheim tunnelling for modelling charge injection into Si3N4 in an Al/Si3N4/Si structure

Charge injection behaviours in silicon nitride of an Al/Si₃N₄/n-Si metal?Cinsulator?Csemiconductor (MIS) device are systematically studied before and after applying different high constant DC bias conditions with the aim of controlling charge accumulation in the dielectric when a high actuation voltage is applied. We found that both polarity and magnitude of charge accumulation in silicon nitride depend on the biasing direction. Charge injection from the semiconductor to the silicon nitride always dominates over charge injection from the Al electrode to the silicon nitride. Negative charge accumulation happens in silicon nitride when the Al electrode is positively biased, and positive charge accumulation occurs in silicon nitride when the Al electrode is negatively biased. The positive charge accumulation is much bigger than the negative charge accumulation under the same magnitude of stress voltage. Furthermore, the experimental results also show that the charge injection level exponentially increases with the applied voltage across the silicon nitride. These observed experimental results can be well explained by a modified Fowler?CNordheim tunnelling charge injection model, which takes into account the roles of both electrons and holes in the process of charge injection.