基于p+-Si与n-ZnO纳米线的p-n异质结的制备及其性质研究

利用CVD蒸汽俘获法，在p^＋硅片上制备了垂直生长的n型ZnO纳米线阵列，用XRD和SEM分析了样品的结构与形貌。测试发现样品的I-V曲线符合典型的p-n异质结特性，正向开启电压为0．5V，反向饱和电流为0．02mA。计算了异质结的理想因子η，发现当异质结两端偏压在0V-0．3V的低压区域，理想因子为1．85，而在0．3v-0．8v的高偏压区域，理想因子为8．36。解释了理想因子偏高的原因是由于金属一半导体接触以及ZnO纳米线与p^＋-si界而存在缺陷。     

MBE n-ZnO/MOCVD p-GaN heterojunction light-emitting diode

The growth, fabrication, and subsequent electroluminescence (EL) characterization of an n-ZnO/p-GaN heterojunction light-emitting diode prepared on c-Al₂O₃ substrate are presented. The diode-like I-V characteristics and room temperature EL spectrum with an intense broadband emission in the yellow-green spectral region has been observed with forward bias applied. Photoluminescence (PL) and Raman spectra of the n-ZnO and p-GaN films were also measured. By comparing PL and EL spectra, it was concluded that the deep-level defect-related emission mainly originated from the GaN epitaxial layer.     

Fabrication of a n-ZnO/p-Si heterojunction diode by ultra-high vacuum magnetron sputtering

Heterojunction diodes of n-type ZnO were fabricated on a p-type Si(100) substrate using an ultra-high vacuum radio frequency magnetron sputtering method at room temperature. A short-time post-annealing process was performed to prevent inter-diffusion of Zn, dopants, and Si atoms. The post-annealing process at 600 °C enhanced the crystallinity of ZnO films and produced a high forward to reverse current ratio of the heterojunction diode with a barrier height of approximately 0.336 eV. A thin SiO_x layer at the interface of the ZnO film and Si substrate appeared distinctly at the 600 °C annealing, however the post-annealing at 700 °C showed an a-(Zn_2xSi_1 − xO₂) structure caused by diffusion of silicon into the ZnO film. In the n-ZnO/p-Si sample annealed at 700 °C, a rapid change in the barrier height was considered due to the effect of the dopant segregation from the substrate and deformation of the a-SiO_x structure.     

Transparent p/n diode device from a single zinc nitride sputtering target

Zinc oxide (ZnO) thin films showing bipolar conductivity were fabricated by sputtering of zinc nitride target in plasma containing mixture of Ar-O₂ gasses. Sputtering in pure Ar plasma produced conductive and opaque zinc nitride (ZnN) films while upon introduction of oxygen up to 30% into the plasma highly transparent single phase polycrystalline n-type ZnO films have been grown. ZnN sputtering in Ar plasma containing more than 30% oxygen produced p-type ZnO films. Hall-effect and photoluminescence measurements revealed the presence of zinc vacancies and nitrogen which are acting as acceptor dopants in p-type ZnO. A heterostructure was fabricated in a single deposition run consisting of n-ZnN and p-ZnO which exhibited rectifying behavior with 2-2.5 V turn-on voltage. Improvements on the formed p/n heterostructure as well as the potential of using single sputtering target in fabrication of Zn-based homo- and hetero-junctions are discussed.     

Bottom-up fabrication of n-ZnO-based memristor and p-Cu2O/n-ZnO heterojunction diode using electroless deposition

Journal of Materials Science: Materials in Electronics - This study introduces a low-cost and feasible electroless deposition technique utilized to fabricate an n-ZnO-based memristor and...     

Schottky diode fabricated on a single crystalline diamond rod

The fabrication process of Al/diamond Schottky diodes on single crystalline diamond rods (SCDRs) was demonstrated. SCDRs of submicron diameters were obtained by etching a polished polycrystalline diamond film in oxygen plasma. The as-scratched SCDR was confirmed to be single crystalline diamond by electron diffraction measurements showing the same fuzzy spot pattern at different parts of an SCDR. Each SCDR was extracted from a grain in the polycrystalline film where the grain size served as a limit of the length of an SCDR. Al/Ti and Al metals were deposited to form ohmic and Schottky contacts, respectively. A hydrogen plasma treatment is an essential step prior to the formation of an Al/diamond Schottky contact in order to improve the device performance. The submicron scale Al/diamond Schottky diode exhibits a very high current density of 1.4 × 10(4) A cm(-2) at a forward bias (V(F)) voltage of - 3 V.     

Current-injection-based 12-pulse rectifier using a single three-phase diode bridge

A three-phase rectifier that applies current injection to reduce the input current total harmonic distortion (THD) is proposed. The rectifier injects rectangular current, which results in the waveforms of the input currents the same as in the case of 12-pulse rectifiers, with the THD equal to 15.22%. The current injection system applies a voltage-loaded resistance emulator. To simplify the rectifier analysis, an equivalent circuit of the rectifier is derived, which significantly reduces the number of nonlinear elements. Analytical optimisation of the resistance emulator transformer turns ratio is performed for the case when the losses in the current injection system can be neglected. Influence of the losses in the current injection system is analysed numerically, and it is shown that they considerably affect the rectifier performance and design. Numerical optimisation of the resistance emulator turns ratio in the presence of losses is performed. Analytical results are experimentally verified on a rectifier with a rated power of 3 kW     

Defects in TiO2 films on p+-Si studied by positron annihilation spectroscopy

Variable-energy positron annihilation spectroscopy has been applied to the study of defects in TiO₂/p⁺-Si structures, in the as-grown state and after annealing in vacuum and in hydrogen, to investigate whether annealing (and film thickness) resulted in an increase of vacancy-type defects in the oxide films. It was found that the concentration of such defects remained unchanged after vacuum annealing for all films studied, but after H₂ annealing more than doubled for 150 nm-thick films, and increased by an order of magnitude for 100 nm-thick films. The nature of the vacancies was examined further by measuring high-precision annihilation lines and comparing them with a reference Si spectrum. The changes observed in the ratio spectra associated with oxygen electrons suggest that the defects are oxygen vacancies, which have been shown to enhance electroluminescence from TiO₂/p⁺-Si heterostructure-based devices.     

Observation of a negative characteristic temperature for the threshold current of diode lasers for the 2.8 /gmm spectral range

A decrease in the lasing threshold with increasing temperature has been observed in InAs/InAsSbP laser heterostructures for the 2.7–2.9 μm spectral range at cryogenic temperatures (T=32–85 K). At temperatures below 50 K a negative characteristic temperature, T ₀=−70 K, was obtained for the threshold current. Characteristics of the temperature dependence of the threshold current and the laser output power were investigated. Pis#x2019;ma Zh. Tekh. Fiz. 23, 72–79 (November 26, 1997)     

Uncertainty quantification in deterministic parameterization of single diode model of a silicon solar cell

Optimization and Engineering - The paper presents a probabilistic approach to study uncertainty quantification in electrical parameters associated with single diode model of a solar cell. Five...     

Fast divalent ion conduction in Ba++, Cd++ and Sr++ beta″ aluminas

Single crystals of Ba⁺⁺, Cd⁺⁺ and Sr⁺⁺ beta″ alumina were prepared from sodium beta″ alumina by ion exchange. The conductivities of these divalent ion solid electrolytes exceed 10^?3 (ohm-cm)^?1 at 300°C. These compounds appear to exhibit fast divalent ion motion at moderate temperatures.     

Preparation of bismuth oxyiodides and oxides and their photooxidation characteristic under visible/UV light irradiation

Bismuth oxyiodides and oxides were prepared by a solution combination with thermal treatment method. The prepared samples were characterized by X-ray diffraction, thermogravimetry, scanning electron microscopy, transmission electron microscopy, and UV-vis diffuse reflectance spectra, and Brunauer-Emmett-Teller surface areas. The photooxidation activity of the samples was evaluated by photocatalytic decolorization of acid orange II under both visible light (λ > 420 nm) and UV light (λ = 365 nm) irradiation. Results show that a series of changes in the compounds take place during the course of calcination, described as: BiOI → Bi₅O₇I → α-Bi₂O₃. Under visible light irradiation, the photocatalytic activities follow the order: BiOI > Bi₅O₇I > Bi₅O₇I/Bi₂O₃ mixture > Bi₂O₃, which is mainly attributed to the different absorption ability to visible light due to the different band gap energy; the activities are in the order: BiOI < Bi₂O₃ < Bi₅O₇I/Bi₂O₃ mixture < Bi₅O₇I under UV light irradiation, which is mainly caused by the different oxidability.     

Negative differential resistance of a tunnel diode induced by an external microwave signal

An experimentally observed effect is described in which a section of negative differential resistance appears on the current-voltage characteristic of a tunnel diode exposed to an external microwave signal when the diode bias voltage in the absence of the microwave signal is substantially below the peak value. The measurements were made for signal frequencies in the range 25–140 GHz. Pis’ma Zh. Tekh. Fiz. 25, 39–42 (January 26, 1999)     

Dramatically enhanced ultraviolet photosensing mechanism in a n-ZnO nanowires/i-MgO/n-Si structure with highly dense nanowires and ultrathin MgO layers

This study reports that the visible-blind ultraviolet (UV) photodetecting properties of ZnO nanowire based photodetectors were remarkably improved by introducing ultrathin insulating MgO layers between the ZnO nanowires and Si substrates. All layers were grown without pause by metal organic chemical vapor deposition and the density and vertical arrangement of the ZnO nanowires were strongly dependent on the thickness of the MgO layers. The sample in which an MgO layer with a thickness of 8 nm was inserted had high density nanowires with a vertical alignment and showed dramatically improved UV photosensing performance (photo-to-dark current ratio = 1344.5 and recovery time = 350 ms). The photoresponse spectrum revealed good visible-blind UV detectivity with a sharp cut off at 378 nm and a high UV/visible rejection ratio. A detailed discussion regarding the developed UV photosensing mechanism from the introduction of the i-MgO layers and highly dense nanowires in the n-ZnO nanowires/i-MgO/n-Si substrates structure is presented in this work.     

Generation of single short tunable UV pulses using a simple short-cavity dye laser

Generation of single, short, tunable UV pulses using a short-cavity dye laser (SCDL) with a novel simple cavity structure is described. A single 80-ps pulse has been obtained at the 616-nm wavelength from a rhodamine 640 dye laser pumped with a 2-ns N2 laser pulse. By amplifying and subsequent frequency-doubling, a 90-ps 308-nm pulse was generated, which can be used as a short-duration XeCl excimer laser source. The temporal characteristics coupled rate equations.     

Physical mechanism of blue-shift of UV luminescence of a single pencil-like ZnO nanowire

Cathodoluminescence spectroscopy is used to address the ultraviolet (UV) luminescence of a single pencil-like ZnO nanowire whose diameter gradually reduces from bottom to top in the range of 700-50 nm. It is found that the UV emission energy evidently shifts to the high energy with the ZnO nanowire's diameter decreasing and the blue-shift of 90 meV is observed when the nanowire diameter reduces to 50 from 700 nm. The physical mechanism of the UV blue-shift of the ZnO nanowire is attributed to the Burstein-Moss effect under the high carrier concentration.     

Effect of diode wavelength broadening in a diode end-pumped solid-state amplifier

The effect of the spectral broadening in cw diode pumping and the wavelength shift in pulsed pumping of a solid-state laser is investigated theoretically. A very simple model allowing the computation of the reduction of the absorbed pump energy is developed. The results are applied to an ytterbium-doped solid-state laser and should be fruitful for amplifier and laser design.     

Synchronisation and chaos in a laser diode driven by a resonant tunnelling diode

The authors report on a hybrid integration of a resonant tunnelling diode laser diode driver configuration that can operate as a self-oscillating circuit, and when externally perturbed shows regions of frequency division and frequency multiplication, quasi-periodic and chaotic oscillations, both in the optical and electrical outputs. The authors also demonstrate that this optoelectronic circuit is well described as a Lienard?s oscillator. The synchronisation capabilities of the circuit have potentially novel functions for optical communications systems including clock recovery, clock division and data encryption.     

The coupling influence of UV illumination and strain on the surface potential distribution of a single ZnO micro/nano wire

Interface/surface properties play an important role in the development of most electronic devices. In particular, nanowires possess large surface areas that create new challenges for their optoelectronic applications. Here, we demonstrated that the piezoelectric field and UV laser illumination modulate the surface potential distribution of a bent ZnO wire by the Kelvin probe force microscopy technology. Experiments showed that the surface potential distribution was changed by strain. The difference of surface potential between the outer/inner sides of the ZnO wire increased with increasing strain. Under UV laser illumination, the difference of surface potential between the outer/inner sides of the ZnO wire increased with increasing strain and illumination time. The origin of the observed phenomenon was discussed in terms of the energy band diagram of the bent wire and adsorption/desorption theory. It is suggested that the change of surface potential can be attributed to the uneven distribution of the carrier density across the wire deduced by the piezoelectric effect and surface adsorption/desorption of oxygen ions. This study provides an important insight into the surface and piezoelectric effects on the surface potential and can help optimize the performance of electronic and optoelectronic devices.

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