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Temperature dependent direct-bandgap light emission and optical gain of Ge

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Chinese Physics B 2016年第5期25卷 400-404页

作者：刘智何超张东亮李传波薛春来左玉华成步文 State Key Laboratory on Integrated Optoelectronics Institute of Semiconductors Chinese Academy of Sciences

Band structure, electron distribution, direct-bandgap light emission, and optical gain of tensile strained, n-doped Ge at different temperatures were calculated. We found that the heating effects not only increase the electron occupancy rate in the Γ valley of Ge by thermal excitation, but also reduce the energy difference between its Γ valley and L valley. However,the light emission enhancement of Ge induced by the heating effects is weakened with increasing tensile strain and n-doping concentration. This phenomenon could be explained by that Ge is more similar to a direct bandgap material under tensile strain and n-doping. The heating effects also increase the optical gain of tensile strained, n-doped Ge at low temperature, but decrease it at high temperature. At high temperature, the hole and electron distributions become more flat, which prevent obtaining higher optical gain. Meanwhile, the heating effects also increase the free-carrier absorption. Therefore, to obtain a higher net maximum gain, the tensile strained, n-doped Ge films on Si should balance the gain increased by the heating effects and the optical loss induced by the free-carrier absorption.

关键词： Ge light emission optical gain

Ultrafast blue light emission from SiC nanowires

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Chinese Optics Letters 2007年第3期5卷 184-186页

作者：赵福利陈洪新邓少芝许宁生贾天卿徐至展 State Key Laboratory of Optoelectronic Materials and Technologies Sun Yat-Sen University

Cubic silicon carbide （SIC） nanowires are synthesized in a catalyst-assisted process. The nanowires with diameter of ～ 40 nm exhibit strong blue light emission at room temperature under ultraviolet （UV） femtosecond laser excitation. The photon energy of peak emission is higher than the energy bandgap of cubic SiC which shows involvement of quantum confinement effect. The ultrafast fluorescence is deconvoluted by Monte-Carlo method. The results show two ultrafast decay processes whose lifetimes are about 26 and 567 ps respectively. The mechanisms of such ultrafast processes are discussed.

关键词： Energy gap Fluorescence Laser excitation light emission Monte Carlo methods Nanowires Quantum confinement

Image charge effect on the light emission of rutile TiO2(110) induced by a scanning tunneling microscope

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Chinese Physics B 2018年第7期27卷 158-162页

作者： Chaoyu Guo Xiangzhi Meng Qin Wang Ying Jiang International Center for Quantum Materials School of Physics Peking University Beijing 100871 China Collaborative Innovation Center of Quantum Matter Beijing 100871 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100049 China

The plasmon-enhanced light emission of rutile TiO2（110） surface has been investigated by a low-temperature scanning tunneling microscope （STM）. We found that the photon emission arises from the inelastic electron tunneling between the STM tip and the conduction band or defect states of TiO2（110）. In contrast to the Au（111） surface, the maximum photon energy as a function of the bias voltage clearly deviates from the linear scaling behavior, suggesting the non-negligible effect of the STM tip on the band structure of TiO2. By performing differential conductance （dl/dV） measurements, it was revealed that such a deviation is not related to the tip-induced band bending, but is attributed to the image charge effect of the metal tip, which significantly shifts the band edges of the TiO2（110） towards the Femi level （EF） during the tunneling process. This work not only sheds new lights onto the understanding of plasmon-enhanced light emission of semiconductor surfaces, but also opens up a new avenue for engineering the plasmon-mediated interfacial charge transfer in molecular and semiconducting materials.

关键词： scanning tunneling microscopy light emission TiO2 plasmon

Limits on light emission from silicon

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Chinese Optics Letters 2009年第4期7卷 268-270页

作者： Peter Würfel Institut für Angewandte Physik Universitt KarlsruheD-76128 KarlsruheGermany

Although silicon is an indirect semiconductor, light emission from silicon is governed by the same gener- alized Planck＇s radiation law as the emission from direct semiconductors. The emission intensity is given by the absorptance of the volume in which there is a difference of the quasi Fermi energies. A difference of the Fermi energies may result h＇om the absorption of external light （photoluminescence） or from the injection of electrons and holes via selective contacts （electroluminescence）. The quantum efficiency may be larger than 0.5 for carrier densities below 10^15 cm^-3. At larger densities, non-radiative recombination, in particular Auger recombination dominates. At all carrier densities, the relation between emission intensity and difference of the quasi Fermi energies is maintained. Since this difference is equal to the voltage of a properly designed solar cell, luminescence is the key indicator of material quality for solar cells.

关键词： Carrier concentration Fermi level light light emission Photoluminescence Semiconducting silicon Silicon

Room-temperature light emission from an airbridge double-heterostructure microcavity of Er-doped Si photonic crystal

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Optoelectronics Letters 2016年第1期12卷 47-51页

作者：王玥安俊明吴远大胡雄伟 State Key Laboratory on Integrated Optoelectronics Institute of SemiconductorsChinese Academy of Sciences

We experimentally demonstrate an efficient enhancement of luminescence from two-dimensional(2D) hexagonal photonic crystal(PC) airbridge double-heterostructure microcavity with Er-doped silicon(Si) as light emitters on siliconon-insulator(SOI) wafer at room temperature.A single sharp resonant peak at 1 529.6 nm dominates the photoluminescence(PL) spectrum with the pumping power of 12.5 m *** obvious red shift and the degraded quality factor(Q-factor) of resonant peak appear with the pumping power increasing,and the maximum measured Q-factor of 4 905 is achieved at the pumping power of 1.5 m *** resonant peak is observed to shift depending on the structural parameters of PC,which indicates a possible method to control the wavelength of enhanced luminescence for Si-based light emitters based on PC microcavity.

关键词： Erbium light light emission Luminescence Microcavities Photonic crystals Q factor measurement Silicon

Surface plasmon-enhanced amorphous-silicon-nitride light emission with single-layer gold waveguides

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Chinese Optics Letters 2013年第2期11卷 88-90页

作者：陈可勇冯雪黄栩东 State Key Laboratory of Integrated Optoelectronics Department of Electronic EngineeringTsinghua University

Surface-plasmon （SP） enhancement of amorphous-silicon-nitride （a-SiNx） light emission with single-layer gold （Au） waveguides is experimentally demonstrated through time-resolved photoluminescence measure- ment. The a-SiN~ active layer with strong steady-state photoluminescence at 560 nm is prepared by plasma-enhanced chemical vapor deposition, and ricated by magnetron sputtering. The maximum the Au waveguide on the top of the a-SiNx layer is lab- Purcell factor value of -3 is achieved with identified SP resonance of the Au waveguide at -530 nm.

关键词： Gold light emission Photoluminescence Plasma enhanced chemical vapor deposition Plasmons Silicon Silicon nitride Waveguides

Internal energy transfer phenomenon and light-emission properties of γ-LiAlO_2 phosphor doped with Mn^(2+)

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International Journal of Minerals,Metallurgy and Materials 2013年第7期20卷 678-683页

作者： Bai-Bin Wang Chi-Fen Chang Wein-Duo Yang Department of Chemical and Materials Engineering Kaohsiung University of Applied Sciences Electronics Testing Center

γ-LiAlO2 phosphor was synthesized using the cellulose-citric acid sol-gel method, and its light emission and energy transfer properties were investigated. Excitation and emission spectrum analysis revealed a decrease in intensity of the spectrum as the amount of Mn2＋ doping increased. Blasse＇s equation determined the maximum distance for energy transfer between Mn2＋ ions as 4.3142 nm. Dexter＇s theory verifies that the mechanism of energy transfer between Mn2＋ ions conforms to an electric dipole and electric quadrupole interaction.

关键词： phosphor energy transfer light emission sol-gel process doping

light-emission organic solar cells with MoO_(3):Al interfacial layer-preparation and characterizations

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Frontiers of Optoelectronics 2021年第4期14卷 499-506页

作者： Xinran LI Yanhui LOU Zhaokui WANG College of Energy Key Laboratory of Advanced Carbon Materials and Wearable Energy Technologies of Jiangsu ProvinceSoochow UniversitySuzhou 215006China Institute of Functional Nano&Soft Materials(FUNSOM) Soochow UniversitySuzhou 215123China

A light-emitting organic solar cell(LE-OSC)with electroluminescence(EL)and photovoltaic(PV)properties is successfully fabricated by connecting the EL and PV units using a MoO_(3):Al co-evaporation interfacial layer,which has suitable work function and good *** and EL units are fabricated based on poly(3-hexylthiophene)(P3HT)-indene-C60 bisadduct(IC60BA)blends,and 4,4′-bis(N-carbazolyl)biphenyl-factris(2-phenylpyridine)iridium(Ir(ppy)3),*** work function and the transmittance of the MoO_(3):Al co-evaporation are measured and adjusted by the ultraviolet photoelectron spectroscopy and the optical spectrophotometer to obtain the better bi-functional device *** forward-and reverse-biased current density-voltage characteristics in dark and under illumination are evaluated to better understand the operational mechanism of the LE-OSCs.A maximum luminance of 1550 cd/m^(2)under forward bias and a power conversion efficiency of 0.24%under illumination(100 mW/cm^(2))are achieved in optimized *** proposed device structure is expected to provide valuable information in the film conditions for understanding the polymer blends internal conditions and meliorating the film qualities.

关键词： organic solar cell(OSC) polymer-fullerene light emission MoO_(3):Al interfacial layer

Analysis of directional emission in square resonator lasers with an output waveguide

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Chinese Optics Letters 2007年第8期5卷 463-465页

作者：赵伟黄永箴 State Key Laboratory on Integrated Optoelectronics Institute of Semiconductors Chinese Academy of Sciences

Square microcavity laser with an output waveguide is proposed and analyzed by the finite-difference time-domain （FDTD） technique. For a square resonator with refractive index of 3.2, side length of 4μm, and output waveguide of 0.4μm width, we have got the quality factors （Q factors） of 6.7 ×10^2 and 7.3 × 10^3 for the fundamental and first-order transverse magnetic （TM） mode near the wavelength of 1.5μm, respectively. The simulated intensity distribution for the first-order TM mode shows that the coupling efficiency in the waveguide reaches 53%. The numerical simulation shows that the first-order transverse modes have fairly high Q factor and high coupling efficiency to the output waveguide. Therefore the square resonator with an output waveguide is a promising candidate to realize single-mode directional emission microcavity lasers.

关键词： Computer simulation Finite difference time domain method Laser modes light emission Refractive index