氮化镓肖特基结紫外探测器的异常特性测量

测量了CaN肖特基结紫外探测器在有、无光照下的I-V异常特性。分别用362nm和368nm光束对有源区进行横向扫描,得到了光照不同部位时探测器在无偏压、2V反向偏压下的电流。紫外光照到肖特基结压焊电极附近及透明电极边沿附近区域时,探测器在反向偏压下有较大增益,空间响应均匀性变差,在禁带内有两个增益响应峰波长——364nm和368nm。探测器在810nm光照射下,反向偏压下的光响应增益、持续光电导存在光淬灭现象。探测器紫外光照完后,俘获中心及表面陷阱所俘获的部分电荷在高反向偏置电压下老化可以通过隧穿或发射效应释放出来,经过高反向偏置电压老化完后的探测器在同一低反向偏置电压下暗电流比老化前的要小。测量结果为GaN器件的研制提供了参考数据。     

GaN-Based Solar-Ultraviolet Detection Instrument

We report on the fabrication of a solar-UV monitoring system that uses GaN-based photodetectors. GaN photoconductors, p-n junction photodiodes, and Schottky barrier photodiodes have been fabricated and characterized as UV sensors. The best performances are obtained in Schottky photodiodes, which show a linear response, a flat responsivity of 100 mA/W, a visible rejection ratio higher than 10(3), and a noise-equivalent power of 1 nW/Hz(-1/2). Preliminary data on Al(x)Ga(1-x)N (x = 0.15, 0.22) detectors are also presented. Using GaN Schottky diodes, we fabricate and evaluate a complete solar-UV detection head.     

肖特基型光催化剂研究进展

贵金属与半导体复合形成的催化剂具备肖特基结结构,该结构具有整流特性和较低的界面电压,可以调控光生电子的产生和流向,使电子和空穴更有效地分离,提升光催化性能.综述了近年来肖特基半导体光催化剂的研究进展,分析了晶面沉积、形貌结构、表面等离子体效应及共掺杂等因素对该类催化剂性能的影响,从降解污染物、制氢、二氧化碳还原等方面阐述了这类催化剂在环境控制领域的实际应用,并提出了势垒高度、产物控制及催化剂循环利用等潜在的研究方向.肖特基型光催化剂独特的性质将使其成为新的研究热点,得到更深入的研究和应用.     

肖特基型光催化剂研究进展

贵金属与半导体复合形成的催化剂具备肖特基结结构,该结构具有整流特性和较低的界面电压,可以调控光生电子的产生和流向,使电子和空穴更有效地分离,提升光催化性能。综述了近年来肖特基半导体光催化剂的研究进展,分析了晶面沉积、形貌结构、表面等离子体效应及共掺杂等因素对该类催化剂性能的影响,从降解污染物、制氢、二氧化碳还原等方面阐述了这类催化剂在环境控制领域的实际应用,并提出了势垒高度、产物控制及催化剂循环利用等潜在的研究方向。肖特基型光催化剂独特的性质将使其成为新的研究热点,得到更深入的研究和应用。     

Gate‐Tunable Graphene–WSe2 Heterojunctions at the Schottky–Mott Limit

Metal–semiconductor interfaces, known as Schottky junctions, have long been hindered by defects and impurities. Such imperfections dominate the electrical characteristics of the junction by pinning the metal Fermi energy. Here, a graphene–WSe₂ p‐type Schottky junction, which exhibits a lack of Fermi level pinning, is studied. The Schottky junction displays near‐ideal diode characteristics with large gate tunability and small leakage currents. Using a gate electrostatically coupled to the WSe₂ channel to tune the Schottky barrier height, the Schottky–Mott limit is probed in a single device. As a special manifestation of the tunable Schottky barrier, a diode with a dynamically controlled ideality factor is demonstrated.     

石墨烯/n-Si肖特基结太阳能电池的性能限制因素及效率提升方法

石墨烯是一种新型的零带隙、半金属材料,具有高透光率,良好的电导率,高稳定性及力学性能,可替代传统的ITO用于制备新一代石墨烯/n-Si肖特基结太阳能电池。详细表述了目前石墨烯/n-Si肖特基结太阳能电池的研究进展,重点总结分析了影响石墨烯/n-Si肖特基结太阳能电池性能的原因及相关的优化方法,为将来进一步对石墨烯/n-Si肖特基结太阳能电池的研究与应用提供借鉴。     

Polarization-induced pn diodes in wide-band-gap nanowires with ultraviolet electroluminescence

Almost all electronic devices utilize a pn junction formed by random doping of donor and acceptor impurity atoms. We developed a fundamentally new type of pn junction not formed by impurity-doping, but rather by grading the composition of a semiconductor nanowire resulting in alternating p and n conducting regions due to polarization charge. By linearly grading AlGaN nanowires from 0% to 100% and back to 0% Al, we show the formation of a polarization-induced pn junction even in the absence of any impurity doping. Since electrons and holes are injected from AlN barriers into quantum disk active regions, graded nanowires allow deep ultraviolet LEDs across the AlGaN band-gap range with electroluminescence observed from 3.4 to 5 eV. Polarization-induced p-type conductivity in nanowires is shown to be possible even without supplemental acceptor doping, demonstrating the advantage of polarization engineering in nanowires compared with planar films and providing a strategy for improving conductivity in wide-band-gap semiconductors. As polarization charge is uniform within each unit cell, polarization-induced conductivity without impurity doping provides a solution to the problem of conductivity uniformity in nanowires and nanoelectronics and opens a new field of polarization engineering in nanostructures that may be applied to other polar semiconductors.     

Wearable and Ultrasensitive Strain Sensor Based on High‐Quality GaN pn Junction Microwire Arrays

With the rapid growth in wearable electronics sensing devices, flexible sensing devices that monitor the human body have shown great promise in personalized healthcare. In the study, high‐quality GaN pn junction microwire arrays with different aspect ratios and large‐area uniformity are fabricated through an easy, repeatable fabrication process. The piezoelectric coefficient (d₃₃) of GaN pn junction microwire arrays increases from 7.23 to 14.46 pm V^?1 with the increasing of the aspect ratio, which is several times higher than that of GaN bulk material. Furthermore, flexible ultrasensitive strain sensor based on GaN microwires with the highest d₃₃ is demonstrated to achieve the maximum open circuit voltage of 10.4 V, and presents excellent durability with stable output signals over 10 000 cycles with a response time of 50 ms. As a flexible and wearable sensor attached to the human skin, the GaN microwire pn junction arrays with such a high degree of uniformity can precisely monitor subtle human pulse and motions, which show great promise in future personalized healthcare.     

Barrier optimization of metal-semiconductor junctions for high power Schottky rectifiers

Metals and their silicides form with n-silicon potential barriers in the 0.5–0.85 eV energy interval. The results of this work determine the barrier height as a very important parameter in the design of high power Schottky diodes. Using the basic relation of one Schottky junction the thermal losses in the junction are optimised and the thermodynamic equilibrium conditions are determined as a function of the barrier height. The analysis concentrates on Schottky junctions that silicon forms with electron-beam-deposited thin films of Cr, Mo, Pd and Pt. The formation of Schottky junctions and the effect of some technological parameters such as substrate temperature during film deposition, Ar ion precleaning of the substrate and thermal annealing of the deposited films are also discussed.     

A transparent photovoltaic device of NiO/MgO quantum dots/TiO2 arrays pn junction with carrier injection of MgO QDs

Journal of Materials Science: Materials in Electronics - A transparent photovoltaic device of NiO/MgO QDs/TiO2 array pn junction was fabricated via a continuous hydrothermal-hydrolysis-sputtering...     

Quantum efficiency of 4H-SiC detectors within the range of 114–400 nm

Technical Physics Letters - Electrical and spectrometric characteristics of 4H-SiC detectors with Cr Schottky barriers in the spectral ranges of 114–175 and 210–400 nm are studied. It...     

Nickel Schottky junction on epi-Ge for strained Ge metal-oxide-semiconductor field-effect transistors source/drain engineering

In this study, the nano-scale epi-Ge/Si fabrication and the Schottky junction source/drain manufacture with Ni incorporation are demonstrated. The Ni Schottky junction formation by laser annealing (LA) and rapid thermal annealing, as well as the barrier height and interface characteristics, are discussed. Improvement in the density of interface trap (D_it) can be achieved by LA; this technology enhances the opportunity of high Ge concentration SiGe channel to play a part in the next-generation complementary metal-oxide-semiconductor applications.     

GaAs Schottky Barrier Detectors for Alpha-Particle Spectrometry at Temperatures up to 120°C

Technical Physics Letters - GaAs Schottky barrier detectors for α particle spectrometry have been tested. Detectors had an input window area of 80 mm2 and a working barrier layer thickness of...     

Characterization of Pt/a-plane GaN Schottky contacts using conductive atomic force microscopy

We investigated the local electrical properties of Pt Schottky contacts to a-plane n-type GaN using conductive atomic force microscopy (C-AFM). Current-voltage characteristics obtained by C-AFM showed rectifying properties, indicating nano-scale Schottky junction formation. Two-dimensional current maps revealed that the surface microstructures of GaN influenced transport properties of the junctions.     

The analysis of the transmission-type optical smoke detector threshold sensitivity to the high rate temperature variations

Reliability of the transmission-type optical smoke detectors is limited by the high sensitivity of optical components to parasitic effects, especially to contamination and temperature. Influences of the high rate temperature variations cannot be eliminated by filtering, as their spectral range partially overlaps with the spectral range of a smoke absorption index. Hence, sensitivity to these effects has to be eliminated through the mutual cancellation of the corresponding components of the output signal. First determining the temperature dependence of the light source and the receiver in the generalized block diagram of the transmission-type optical smoke detector, transfer functions are derived, specifying the detector output signal as a function of the temperature variations of the blocks considered. Using the second-order thermal model for the thermal system of the optoelectronic diodes, an expression is given for the steady-state solution of the difference of the source and the receiver diode junction temperatures, when the ambient temperature is a ramp function of time. On the basis of the thermal system analysis, a block diagram is shown to be equivalent to RC low-pass (LP) filters that model the pn junction temperature dependence on ambient temperature. For the completed block diagram, with the help of the expressions derived, an analysis is performed to establish how to eliminate the detector threshold sensitivity to ambient temperature variations, or to adjust it to realize a multicriteria fire detector.     

(PEDOT-PSS)-碳纳米管复合膜硅基太阳能电池

碳纳米管-Si(CNTs-Si)肖特基太阳能电池具有制作简单、成本低的优势。然而,受限于CNTs薄膜的电阻高、结区均匀性差、反光严重等因素,该类器件的光电转换效率仍较低。本文研究了聚3,4-乙撑二氧噻吩-聚苯乙烯磺酸盐(PEDOT-PSS)-CNTs复合透明膜的制备及其在硅太阳能电池中的应用。电流-电压曲线表明,PEDOT-PSS的引入可以大幅度提升CNTs-Si器件的光电转换效率(从5.9%到11.6%)。作为透明电极,复合膜中的取向CNTs可有效地收集和传导太阳能电池结区的光生空穴,而PEDOT-PSS则有效填补了CNTs膜的面内空隙,进而增加了肖特基结的面积。采用表面刻有倒金字塔结构的聚二甲基硅氧烷(PDMS)作为减反层,有效地降低入射光的反射,增加Si表面对光的吸收,进一步将(PEDOT-PSS)-CNTs-Si器件的光电转换效率提升至12.4%。电子束感生电流技术表明器件的光电转换主要基于复合膜与Si之间的肖特基结。     

Investigation of CdTex and Cd1-xZnxTe Schottky Barrier Diode Structure Based γ-Ray Detectors

Cadmium Telluride (CdTe) and Cadmium Zinc Telluride (CdZnTe) based detectors have been developed for hard X-ray and γ -ray detection. These semiconducting materials have high resistivity because of the wide bandgap and also have high photon absorption efficiency because of the large atomic number (Z_Cd = 48, Z_Te = 52). CdTe and CdZnTe substrates (7 mm × 9 mm × 0.5 mm) with different stoichiometry were taken for the fabrication of γ-ray detectors. The substrate was prepared by polishing the bulk crystals grown by the rotational Bridgman method. Crystals with maximum electrical resistivity were grown in this way. For fabrication of Schottky barrier diode structures, the Schottky contacts were made by electroless deposition for gold (Au) and thermal evaporation for Indium (In). The Au/CdTe/In and Au/CdZnTe/In Schottky barrier diodes were linked to the charge sensitive preamplifier by gold wires. Then, I-V measurement and detector efficiency like charge collection performance with energy resolutions were analyzed at room temperature by using ⁵⁷Co and ¹³⁷Cs gamma sources. The good energy resolutions of ⁵⁷Co (122 KeV) and ¹³⁷Cs (662 KeV) sources are obtained for both CdTe and CdZnTe diode detectors.     

Coincidence timing of Schottky CdTe detectors for tomographic imaging

Schottky CdTe detectors are good candidates for large pixel array imagers. For use of such arrays in Positron Emission Tomography (PET) the coincidence timing of the detectors is very important, since it reduces the background from random coincidences. The coincidence timing of a small 2×2×1 mm³ detector has been measured as 11.6 ns, and thus is not much worse than the timing of BGO scintillators, commonly used in PET.     

Junction properties of Schottky diode based on composite organic semiconductors

Composite of polyaniline with polyvinyl chloride (PANI-PVC) has been used for the fabrication of Schottky diode with configuration Pt/PANI-PVC/In. Current-voltage (I-V) plots were non-linear and capacitance-voltage (C-V) plots were almost linear in reverse bias indicating rectification behavior. The observed current-voltage characteristics can be satisfactorily fitted using the modified Schottky equation. Various junction parameters were calculated from the temperature dependent I-V and C-V data and discussed. It has been observation that ideality factor decreases as the temperature increases. Impedance studies shows the R(RC)(RC) equivalent circuit for the fabricated Schottky diode.     

Carbon nanotube Schottky diodes using Ti-Schottky and Pt-Ohmic contacts for high frequency applications

We have demonstrated Schottky diodes using semiconducting single-walled nanotubes (s-SWNTs) with titanium Schottky and platinum Ohmic contacts for high-frequency applications. The diodes are fabricated using angled evaporation of dissimilar metal contacts over an s-SWNT. The devices demonstrate rectifying behavior with large reverse bias breakdown voltages of greater than -15 V. To decrease the series resistance, multiple SWNTs are grown in parallel in a single device, and the metallic tubes are burnt-out selectively. At low biases these diodes showed ideality factors in the range of 1.5 to 1.9. Modeling of these diodes as direct detectors at room temperature at 2.5 terahertz (THz) frequency indicates noise equivalent powers (NEP) potentially comparable to that of the state-of-the-art gallium arsenide solid-state Schottky diodes, in the range of 10(-13) W/ radical Hz.