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Growth and device characteristics of nano-folding InGaN/GaNmultiple quantum well LED
纳米折叠InGaN/GaN LED材料生长及器件特性

Chen Gui-Feng,Tan Xiao-Dong,Wan Wei-Tian,Shen Jun,Hao Qiu-Yan,Tang Cheng-Chun,Zhu Jian-Jun,Liu Zong-Shun,Zhao De-Gang,Zhang Shu-Ming,

物理学报 , 2011,
Abstract: GaN-based LED wafers with nano-folding InGaN/GaN multiple quantum wells (MQWs) are grown on n-GaN nanopillar array templates which are fabricated using self assembled Ni nanodots as etching mask. Photoluminescence (PL) spectra of the wafer show uniform light emission wavelength over the whole area of it. No blue shift of the main peak is observed in the electroluminescence (EL) spectra of the LED devices fabricated with the wafer as the injection current increases from 10 mA to 80 mA. This can be ascribed to the reduced quantum confinement Stark effect (QCSE) and the resulting less band gap tilted by strain relaxation in the nano-folded MQWs. The device shows an excellent rectifying behavior with a forward voltage of 4.6 V under 20 mA injection current.
Dielectric Properties of GaN in THz Frequencies

FANG He-Nan,ZHANG Rong,LIU Bin,LU Hai,DING Jian-Ping,XIE Zi-Li,XIU Xiang-Qian,ZHENG You-Dou,XIAO Ming-Wen,ZHANG Cai-Hong,CHEN Jian,WU Pei-Heng,

中国物理快报 , 2010,
Abstract: The complex refractive indices and the dielectric function of GaN for frequencies ranging from 0.25 to 1.22THz are obtained using THz time-domain spectroscopy. The real part of the dielectric function first decreases from 0.25 to 0.42THz and then oscillates from 0.42 to 1.22THz, whereas the imaginary part of the dielectric function is oscillating within the whole range of frequency. The simple Drude model is extended to take into account the effect of defects on the dielectric function. The extended model is in agreement with the experimental data.
Subwavelength and microstructured planar THz waveguides, theory and experiment  [PDF]
A. Markov,A. Mazhorova,B. Ung,H. Minamide,Y. Wang,H. Ito,M. Skorobogatiy
Physics , 2011,
Abstract: Planar dielectric subwavelength waveguides are proposed as waveguides for THz radiation. The waveguide porous design maximizes the fraction of power guided in the air to avoid the complexity that all the materials are highly absorbent in the THz region. Convenient access to the mode region makes them also useful for sensing of biological and chemical specimens in the THz region.
DNA-based tunable THz oscillator  [PDF]
A. V. Malyshev,V. A. Malyshev,F. Dominguez-Adame
Physics , 2008, DOI: 10.1016/j.jlumin.2009.01.023
Abstract: The intrinsic double helix conformation of the DNA strands is known to be the key ingredient of control of the electric current through the DNA by the perpendicular (gate) electric field. We show theoretically that Bloch oscillations in the DNA are also strongly affected by such lateral field; the oscillation frequency splits into a manifold of several generally non-commensurate frequencies leading to a complicated pattern of the charge motion. The frequency of the oscillations falls in the THz domain, providing for a possibility to design a nano-scale source of THz radiation.
Improved Light Extraction of GaN-based LEDs with Nano-roughened p-GaN Surfaces

GAO Hai-Yong,YAN Fa-Wang,FAN Zhong-Chao,LI Jin-Min,ZENG Yi-Ping,WANG Guo-Hong,

中国物理快报 , 2008,
Abstract: p-GaN surfaces are nano-roughened by plasma etching to improve the optical performance of GaN-based light emitting diodes (LEDs). The nano-roughened GaN present a relaxation of stress. The light extraction of the LEDs withnano-roughened surfaces is greatly improved when compared with that of the conventional LEDs without nano-roughening. PL-mapping intensities of the nano-roughened LED epi-wafers for different roughening times present two to ten orders of enhancement. The light output powers are also higher for the nano-roughened LED devices. This improvement is attributed to that nano-roughened surfaces can provide photons multiple chances to escape from the LED surfaces.
Monte Carlo Calculations of Amplification Spectrum for GaN THz Transit-time Resonance Maser  [PDF]
E. Starikov,P. Shiktorov,V. Gru inskis,L. Reggiani,L. Varani,J. C. Vaissière,Jian H. Zhao
VLSI Design , 2001, DOI: 10.1155/2001/65961
Abstract: We report Monte Carlo calculations of the amplification spectrum of microwave generation in bulk GaN and its dependence on applied electric fields, doping level, lattice temperature, etc. The amplification is shown to occur in a wide frequency range of 0.05 to 3 THz with an optimal generation efficiency of about 1 ∼ 2%.
A planar force-constant model for phonons in wurtzite GaN and AlN: Application to hexagonal GaN/AlN superlattices  [PDF]
Lingjun Wang,Guanghong Wei,Jian Zi
Physics , 1998,
Abstract: A planar force-constant model is developed for longitudinal phonons of wurtzite GaN and AlN propagating along the [0001] direction. The proposed model is then applied to the study of the phonon modes in hexagonal GaN/AlN superlattices in the longitudinal polarization. The confinement of the superlattice phonon mode is discussed.
Planar arrays of magnetic nanocrystals embedded in GaN  [PDF]
A. Navarro-Quezada,T. Devillers,Tian Li,A. Bonanni
Physics , 2012, DOI: 10.1063/1.4747809
Abstract: Single planar arrays of Ga(x)Fe(4-x)N magnetic nanocrystals embedded in GaN have been fabricated in an epitaxial process. The phase of the nanocrystals and their epitaxial relationship with the host matrix are studied $via$ high-resolution transmission electron microscopy and high-resolution x-ray diffraction. By changing the growth parameters and mode, the crystallographic phase and chemical composition of the nanocrystals can be varied on demand. In view of the different magnetic properties of the various phases, applications in room-temperature ferromagnetic as well as antiferromagnetic spintronic devices are envisaged.
Nonpolar m-plane GaN/AlGaN heterostructures with intersubband transitions in the 5 to 10 THz band  [PDF]
C. B. Lim,A. Ajay,C. Bougerol,B. Haas,J. Sch?rmann,M. Beeler,J. L?hnemann,M. Eickhoff,E. Monroy
Physics , 2015, DOI: 10.1088/0957-4484/26/17/175201
Abstract: This paper assesses intersubband transitions in the 1 to 10 THz frequency range in nonpolar m-plane GaN/AlGaN multi-quantum-wells deposited on free-standing semi-insulating GaN substrates. The quantum wells were designed to contain two confined electronic levels, decoupled from the neighboring wells. Structural analysis reveals flat and regular quantum wells in the two perpendicular inplane directions, with high-resolution images showing inhomogeneities of the Al composition in the barriers along the growth axis. We do not observe extended structural defects introduced by the epitaxial process. Low-temperature intersubband absorption from 1.5 to 9 THz is demonstrated, covering part of the 7 to 10 THz band forbidden to GaAs-based technologies.
On the Possibility of THz Amplification and Generation in Nano-Structures, by Means of 2D Plasma Waves  [PDF]
A. V. Chaplik,G. P. Berman
Physics , 2005,
Abstract: We discuss the possibility of THz amplification and generation in nano-structures, by means of 2D plasma waves. Numerical estimates have been made for room temperature and for sufficiently good GaAs materials.
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