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GaN nanopillars with a nickel nano-island mask

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Journal of Semiconductors 2013年第12期34卷 21-25页

作者：林增钦修向前张世英华雪梅谢自力张荣陈鹏韩平郑有炓 Key Laboratory of Advanced Photonic and Electronic Materials School of Electronic Science and EngineeringNanjing University

Uniform GaN nanopillar arrays have been successfully fabricated by inductively coupled plasma etching using self-organized nickel nano-islands as the masks on GaN/sapphire. GaN nanopillars with diameters of 350 nm and densities of 2.6 × 10^8 cm^-2 were demonstrated and controlled by the thickness of Ni film and the NH3 annealing time. These GaN nanopillars show improved optical properties and strain change compared to that of GaN film before ICP etching. Such structures with large-area uniformity and high density could provide additional advantages for light emission of light-emitting diodes, quality improvement of ELO regrowth, etc.

关键词： GaN nanopillars nickel nano-island thermal ammonia etching mask ICP SEM

The enhancement of light-emitting efficiency using GaN-based multiple quantum well light-emitting diodes with nanopillar arrays

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Chinese Physics B 2013年第8期22卷 679-682页

作者：万图图叶展圻陶涛谢自力张荣刘斌修向前李毅韩平施毅郑有炓 Key Laboratory of Advanced Photonic and Electronic Materials School of Electronic Science and Engineering Nanjing University

The quest for higher modulation speed and lower energy consumption has inevitably promoted the rapid development of semiconductor-based solid lighting devices in recent years. GaN-based light-emitting diodes （LEDs） have emerged as promising candidates for achieving high efficiency and high intensity, and have received increasing attention among many researchers in this field. In this paper, we use a self-assembled array-patterned mask to fabricate InGaN/GaN multi- quantum well （MQW） LEDs with the intention of enhancing the light-emitting efficiency. By utilizing inductively coupled plasma etching with a self-assembled Ni cluster as the mask, nanopillar arrays are formed on the surface of the InGaN/GaN MQWs. We then observe the structure of the nanopillars and find that the V-defects on the surface of the conventional structure and the negative effects of threading dislocation are effectively reduced. Simultaneously, we make a comparison of the photoluminescence （PL） spectrum between the conventional structure and the nanopillar arrays, achieved under an experimental set-up with an excitation wavelength of 325 mm. The analysis demonstrates that MQW-LEDs with nanopillar arrays achieve a PL intensity 2.7 times that of conventional LEDs. In response to the PL spectrum, some reasons are proposed for the enhancement in the light-emitting efficiency as follows： 1） the improvement in crystal quality, namely the reduction in V-defects; 2） the roughened surface effect on the expansion of the critical angle and the attenuated total reflection; and 3） the enhancement of the light-extraction efficiency due to forward scattering by surface plasmon polariton modes in Ni particles deposited above the p-type GaN layer at the top of the nanopillars.

关键词： nanopillar arrays InGaN/GaN multiple quantum wells quantum efficiency

Fabrication and Characterization of a GaN-Based 320×256 Micro-LED Array

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Chinese Physics Letters 2017年第11期34卷 98-101页

作者：莫晓帆徐尉宗陆海周东任芳芳陈敦军张荣郑有炓 Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials and School of Electronic Science and EngineeringNanjing UniversityNanjing 210093

Design, fabrication and characterizations of GaN-based blue micro light emitting diode （LED） arrays are reported. The GaN micro-LED array consists of 320×256 pixels with a pitch size of 30μm. Each pixel is 25×25μm^2 in size, which is designed for backside emission and high density flip-chip packaging. The selected LED pixels being tested exhibit good uniformity in terms of turn-on voltage and reverse leakage current. The efficiency droop behavior and reliability behavior under high forward current stress are also studied. The micro-LED pixel shows improved reliability, which is likely caused by enhanced heat dissipation.

关键词： LED GaN Fabrication and Characterization of a GaN-Based 320

Observation of Shubnikov-de Haas Oscillations in Large-Scale Weyl Semimetai WTe2 Films

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Chinese Physics Letters 2020年第1期37卷 64-68页

作者：陈业全陈勇达宁纪爱陈立明庄文卓何亮张荣徐永兵王学锋 Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials School of Electronic Science and Engineeringand Collaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing 210093

Topological Weyl semimetal WTe2 with large-scale Him form has a promising prospect for new-generation spintronic devices.However,it remains a hard task to suppress the defect states in large-scale WTe2 films due to the chemical nature.Here we significantly improve the crystalline quality and remove the Te vacancies in WTe2 films by post annealing.We observe the distinct Shubnikov-de Haas quantum oscillations in WTe2 films.The nontrivial Berry phase can be revealed by Landau fan diagram analysis.The Hall mobility of WTe2 films can reach 1245cm^2V^-1s^-1 and 1423cm^2V^-1s^-1 for holes and electrons with the carrier density of 5× 10^19 cm^-3 and 2 × 10^19 cm^-3,respectively.Our work provides a feasible route to obtain high-quality Weyl semimetal films for the future topological quantum device applications.

关键词： quantum nontrivial remove

Solar-blind ultraviolet band-pass filter based on metal–dielectric multilayer structures

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Chinese Physics B 2014年第7期23卷 404-408页

作者：王天娇徐尉宗陆海任芳芳陈敦军张荣郑有炓 Key Laboratory of Advanced Photonic and Electronic Materials of Jiangsu Province and School of Electronic Science and EngineeringNanjing University

Solar-blind ultraviolet （UV） band-pass filter has significant value in many scientific, commercial, and military appli- cations, in which the detection of weak UV signal against a strong background of solar radiation is required. In this work, a solar-blind filter is designed based on the concept of ＂transparent metal＂. The filter consisting of Al/SiO2 multilayers could exhibit a high transmission in the solar-blind wavelength region and a wide stopband extending from near-ultraviolet to infrared wavelength range. The central wavelength, bandwidth, Q factor, and rejection ratio of the passband are numerically studied as a function of individual layer thickness and multilayer period.

关键词： solar-blind band-pass filter metal-dielectric multilayer

Breakdown characteristics of AlGaN/GaN Schottky barrier diodes fabricated on a silicon substrate

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Chinese Physics B 2014年第9期23卷 414-418页

作者：蒋超陆海陈敦军任芳芳张荣郑有炓 Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials and School of Electronic Science and EngineeringNanjing University

In this work, the breakdown characteristics of AlGaN/GaN planar Schottky barrier diodes （SBDs） fabricated on the silicon substrate are investigated. The breakdown voltage （BV） of the SBDs first increases as a function of the anodeto-cathode distance and then tends to saturate at larger inter-electrode spacing. The saturation behavior of the BV is likely caused by the vertical breakdown through the intrinsic GaN buffer layer on silicon, which is supported by the post-breakdown primary leakage path analysis with the emission microscopy. Surface passivation and field plate termination are found effective to suppress the leakage current and enhance the BV of the SBDs. A high BV of 601 V is obtained with a low on-resistance of 3.15 mΩ·cm^2.

关键词： AlGaN/GaN Schottky barrier diodes silicon substrate breakdown

Forward Current Transport Mechanisms of Ni/Au-InAlN/AlN/GaN Schottky Diodes

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Chinese Physics Letters 2014年第5期31卷 140-143页

作者：王晓风邵振广陈敦军陆海张荣郑有炓 Key Laboratory of Advanced Photonic and Electronic Materials School of Electronic Science and Engineering Nanjing University Nanjing 210093

We fabricate two Ni/Au-In0.17 Al0.83N/AlN/GaN Schottky diodes on substrates of sapphire and Si, respectively, and investigate their forward-bias current transport mechanisms by temperature-dependent current-voltage mea- surements. In the temperature range of 300-485K, the Schottky barrier heights （SBHs） calculated by using the conventional thermionic-emission （TE） model are strongly positively dependent on temperature, which is in contrast to the negative-temperature-dependent characteristic of traditional semiconductor Schottky diodes. By fitting the forward-bias I V characteristics using different current transport models, we find that the tunneling current model can describe generally the I V 5ehaviors in the entire measured range of temperature. Under the, high forward bias, the traditional TE mechanism also gives a good fit to the measured I-V data, and the actual barrier heights calculated according to the fitting TE curve are 1.434 and 1.413eV at 300K for InAlN/AlN/GaN Schottky diodes on Si and the sapphire substrate, respectively, and the barrier height shows a slightly negative temperature coefficient. In addition, a formula is given to estimate SBHs of Ni/Au-InAlN/AlN/GaN Schottky diodes taking the Fermi-level pinning effect into account.

关键词： SCHOTTKY-barrier diodes SCHOTTKY barrier THERMIONIC emission FERMI level ELECTRON mobility DISLOCATION density

Tailoring the Spatial Distribution and Content of Inorganic Nitrides in Solid-Electrolyte Interphases for the Stable Li Anode in Li-S Batteries

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Energy & Environmental materials 2022年第4期5卷 1180-1188页

作者： Qi Jin Kaixin Zhao Lu Li Xinzhi Ma Lili Wu Xitian Zhang key laboratory for photonic and electronic Bandgap materials Ministry of EducationSchool of Physics and Electronic EngineeringHarbin Normal UniversityHarbin 150025China

Among the alternatives to lithium-ion batteries,lithium-sulfur(Li-S)batteries are considered as an attractive option because of their high theoretical energy density of 2570 Wh kg^(−1).However,the application of the Li-S battery has been plagued by the rapid failure of the Li anode due to the Li dendrite growth and severe parasitic reactions between Li and lithium polysulfides.The physicochemical properties of the solid-electrolyte interphase have a profound impact on the performance of the Li anode.Herein,a lithium polyacrylic acid/lithium nitrate(LPL)-protective layer is developed to inhibit the dendrite Li growth and parasitic reactions by tailoring the spatial distribution and content of LiN_(x)O_(y) and Li_(3)N at the SEI.The modified SEI is thoroughly investigated for compositions,ion transport properties,and Li plating/stripping kinetics.Consequently,the Li-S cell with a high S loading cathode(5.0 mg cm^(−2)),LPL layer-protected thin Li anode(50μm),and 40μL electrolyte shows a long life span of 120 cycles.This work evokes the avenue for regulating the spatial distribution of inorganic nitride at the SEI to suppress the formation of Li dendrites and parasitic reactions in Li-S batteries and perhaps guiding the design of analogous battery systems.

关键词： Li anode Li dendrites LiPAA/LiNO_(3)layer SEI shuttle effect

Chemical mechanical polishing of freestanding GaN substrates

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Journal of Semiconductors 2009年第2期30卷 26-29页

作者：颜怀跃修向前刘战辉张荣华雪梅谢自力韩平施毅郑有炓 Key Laboratory of Advanced Photonic and Electronic Materials Department of PhysicsNanjing University

Chemical mechanical polishing （CMP） has been used to produce smooth and scratch-free surfaces for GaN. In the aqueous solution of KOH, GaN is subjected to etching. At the same time, all surface irregularities, including etch pyramids, roughness after mechanical polishing and so on will be removed by a polishing pad. The experiments had been performed under the condition of different abrasive particle sizes of the polishing pad. Also the polishing results for different polishing times are analyzed, and chemical mechanical polishing resulted in an average root mean square （RMS） surface roughness of 0.565 nm, as measured by atomic force microscopy.

关键词： GaN chemical mechanical polishing epitaxial layers