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| Record 1 of 16 |
| Author(s): Wang, YS (Wang YanShuo); Chen, NF (Chen NuoFu); Zhang, XW (Zhang XingWang); Bai, YM (Bai YiMing); Wang, Y (Wang Yu); Huang, TM (Huang TianMao); Zhang, H (Zhang Han); Shi, HW (Shi HuiWei) |
| Title: Analysis of leakage current in GaAs micro-solar cell arrays |
| Source: SCIENCE CHINA-TECHNOLOGICAL SCIENCES, 53 (5): 1240-1246 MAY 2010 |
| Abstract: The output characteristics of micro-solar cell arrays are analyzed on the basis of a modified model in which the shunt resistance between cell lines results in current leakage. The modification mainly consists of adding a shunt resistor network to the traditional model. The obtained results agree well with the reported experimental results. The calculation results demonstrate that leakage current in substrate affects seriously the performance of GaAs micro- solar cell arrays. The performance of arrays can be improved by reducing the number of cells per line. In addition, at a certain level of integration, an appropriate space occupancy rate of the single cell is recommended for ensuring high open circuit voltages, and it is more appropriate to set the rates at 80%-90% through the calculation. |
| ISSN: 1674-7321 |
| DOI: 10.1007/s11431-010-0003-x |
| Record 2 of 16 |
| Author(s): Luo, J (Luo Jing); Zheng, HZ (Zheng HouZhi); Shen, C (Shen Chao); Zhang, H (Zhang Hao); Zhu, K (Zhu Ke); Zhu, H (Zhu Hui); Liu, J (Liu Jian); Li, GR (Li GuiRong); Ji, Y (Ji Yang); Zhao, JH (Zhao JianHua) |
| Title: Ultrafast photo-induced turning of magnetization and its relaxation dynamics in GaMnAs |
| Source: SCIENCE CHINA-PHYSICS MECHANICS & ASTRONOMY, 53 (5): 779-782 MAY 2010 |
| Abstract: We report that, by linearly polarized pumping of different wavelengths, Kerr transients appear at zero magnetic field only in the case when GaMnAs samples are initialized at 3 K by first applying a 0.8 Tesla field and then returning to zero field. We find that, instead of magnetization precession, the near-band gap excitation induces a coherent out-of-plane turning of magnetization, which shows very long relaxation dynamics with no precession. When photon energy increases, the peak value of the Kerr transient increases, but it decays rapidly to the original slow transient seen under the near-band-gap excitation. |
| ISSN: 1674-7348 |
| DOI: 10.1007/s11433-010-0196-9 |
| Record 3 of 16 |
| Author(s): Yang, W (Yang Wei); Luo, HH (Luo Hai-Hui); Qian, X (Qian Xuan); Ji, Y (Ji Yang) |
| Title: STUDY ON MICROWAVE CYCLOTRON RESONANCE OF HIGH-MOBILITY GaAs/Al-0.35 Ga-0.65 As TWO-DIMENSIONAL ELECTRON GAS |
| Source: JOURNAL OF INFRARED AND MILLIMETER WAVES, 29 (2): 87-+ APR 2010 |
| Abstract: The properties of electron states in the presence of microwave irradiation play a key role in understanding the oscillations of longitudinal resistance and the zero-resistance states in a high-mobility two-dimensional electron gas(2DEG) in low magnetic field. The properties of electron states in a high-mobility and low-density GaAs/Al0.35Ga0.65As 2DEG in the presence of Ka-band microwave irradiation were studied by reflectance-based optically detected cyclotron resonance(RODCR). The influences of the direction of microwave alternating electronic field, wavelength of the laser, and temperature on RODCR results were discussed. The results show that RODCR measurements provide a convenient and powerful method for studying electron states in 2DEG. |
| ISSN: 1001-9014 |
| Record 4 of 16 |
| Author(s): You, JB (You, J. B.); Zhang, XW (Zhang, X. W.); Zhang, SG (Zhang, S. G.); Tan, HR (Tan, H. R.); Ying, J (Ying, J.); Yin, ZG (Yin, Z. G.); Zhu, QS (Zhu, Q. S.); Chu, PK (Chu, Paul K.) |
| Title: Electroluminescence behavior of ZnO/Si heterojunctions: Energy band alignment and interfacial microstructure |
| Source: JOURNAL OF APPLIED PHYSICS, 107 (8): Art. No. 083701 APR 15 2010 |
| Abstract: n-ZnO/p-Si heterojunction light-emitting diodes (LEDs) show weak defect-related electroluminescence (EL). In order to analyze the origin of the weak EL, the energy band alignment and interfacial microstructure of ZnO/Si heterojunction are investigated by x-ray photoelectron spectroscopy. The valence band offset (VBO) is determined to be 3.15 +/- 0.15 eV and conduction band offset is -0.90 +/- 0.15 eV, showing a type-II band alignment. The higher VBO means a high potential barrier for holes injected from Si into ZnO, and hence, charge carrier recombination takes place mainly on the Si side rather than the ZnO layer. It is also found that a 2.1 nm thick SiOx interfacial layer is formed at the ZnO/Si interface. The unavoidable SiOx interfacial layer provides to a large number of nonradiative centers at the ZnO/Si interface and gives rise to poor crystallinity in the ZnO films. The weak EL from the n-ZnO/p-Si LEDs can be ascribed to the high ZnO/Si VBO and existence of the SiOx interfacial layer. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3385384] |
| ISSN: 0021-8979 |
| Article Number: 083701 |
| DOI: 10.1063/1.3385384 |
| Record 5 of 16 |
| Author(s): Tang, LM (Tang, Li-Ming); Wang, LL (Wang, Ling-Ling); Wang, D (Wang, Dan); Liu, JZ (Liu, Jian-Zhe); Chen, KQ (Chen, Ke-Qiu) |
| Title: Donor-donor binding in In2O3: Engineering shallow donor levels |
| Source: JOURNAL OF APPLIED PHYSICS, 107 (8): Art. No. 083704 APR 15 2010 |
| Abstract: Using first-principles band structure methods, we investigate the interactions between different donors in In2O3. Through the formation energy and transition energy level calculations, we find that an oxygen-vacancy creates a deep donor level, while an indium-interstitial or a tin-dopant induces a shallow donor level. The coupling between these donor levels gives rise to even shallower donor levels and leads to a significant reduction in their formation energies. Based on the analysis of the PBE0-corrected band structure and the molecular-orbital bonding diagram, we demonstrate these effects of donor-donor binding. In addition, total energy calculations show that these defect pairs tend to be more stable with respect to the isolated defects due to their negative binding energies. Thus, we may design shallow donor levels to enhance the electrical conductivity via the donor donor binding. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3374644] |
| ISSN: 0021-8979 |
| Article Number: 083704 |
| DOI: 10.1063/1.3374644 |
| Record 6 of 16 |
| Author(s): Ji, L (Ji Lian); Zhang, SM (Zhang Shu-Ming); Jiang, DS (Jiang De-Sheng); Liu, ZS (Liu Zong-Shun); Zhang, LQ (Zhang Li-Qun); Zhu, JJ (Zhu Jian-Jun); Zhao, DG (Zhao De-Gang); Duan, LH (Duan Li-Hong); Yang, H (Yang Hui) |
| Title: Fabrication and Characterization of High Power InGaN Blue-Violet Lasers with an Array Structure |
| Source: CHINESE PHYSICS LETTERS, 27 (5): Art. No. 054204 MAY 2010 |
| Abstract: InGaN/GaN multi-quantum-well-structure laser diodes with an array structure are successfully fabricated on sapphire substrates. The laser diode consists of four emitter stripes which share common electrodes on one laser chip. An 800-mu m-long cavity is formed by cleaving the substrate along the < 1 (1) over bar 00 >. orientation using laser scriber. The threshold current and voltage of the laser array diode are 2A and 10.5 V, respectively. A light output peak power of 12W under pulsed current injection at room temperature is achieved. We simulate the electric properties of GaN based laser diode in a co-planar structure and the results show that minimizing the difference of distances between the different ridges and the n-electrode and increasing the electrical conductivity of the n-type GaN are two effective ways to improve the uniformity of carrier distribution in emitter stripes. Two pairs of emitters on a chip are arranged to be located near the two n-electrode pads on the left and right sides, and the four stripe emitters can laser together. The laser diode shows two sharp peaks of light output at 408 and 409 nm above the threshold current. The full widths at half maximum for the parallel and perpendicular far field patterns are 8 degrees and 32 degrees, respectively. |
| ISSN: 0256-307X |
| Article Number: 054204 |
| DOI: 10.1088/0256-307X/27/5/054204 |
| Record 7 of 16 |
| Author(s): Xiao, X (Xiao Xi); Li, YT (Li Yun-Tao); Yu, YD (Yu Yu-De); Yu, JZ (Yu Jin-Zhong) |
| Title: Silicon-Based Asymmetric Add-Drop Microring Resonators with Ultra-Large Through-Port Extinctions |
| Source: CHINESE PHYSICS LETTERS, 27 (5): Art. No. 054208 MAY 2010 |
| Abstract: We theoretically simulate and experimentally demonstrate ultra-large through-port extinctions in silicon-based asymmetrically-coupled add-drop microring resonators (MRs). Through-port responses in an add-drop MR are analyzed by simulations and large extinctions are found when the MR is near-critically coupled. Accurate fabrication techniques are applied in producing a series of 20 mu m-radii add-drop microrings with drop-side gap-widths in slight differences. A through-port extinction of about 42.7 dB is measured in an MR with through-and drop-side gap-width to be respectively 280 nm and 295 nm. The large extinction suggests about a 20.5 dB improvement from the symmetrical add-drop MR of the same size and the through-side gap-width. The experimental results are finally compared with the post-fabrication simulations, which show a gap-width tolerance of > 30 nm for the through-port extinction enhancement. |
| ISSN: 0256-307X |
| Article Number: 054208 |
| DOI: 10.1088/0256-307X/27/5/054208 |
| Record 8 of 16 |
| Author(s): Deng, HX (Deng Hui-Xiong); Jiang, XW (Jiang Xiang-Wei); Tang, LM (Tang Li-Ming) |
| Title: Quantum Mechanical Study on Tunnelling and Ballistic Transport of Nanometer Si MOSFETs |
| Source: CHINESE PHYSICS LETTERS, 27 (5): Art. No. 057101 MAY 2010 |
| Abstract: Using self-consistent calculations of million-atom Schrodinger-Poisson equations, we investigate the I-V characteristics of tunnelling and ballistic transport of nanometer metal oxide semiconductor field effect transistors (MOSFET) based on a full 3-D quantum mechanical simulation under nonequilibtium condition. Atomistic empirical pseudopotentials are used to describe the device Hamiltonian and the underlying bulk band structure. We find that the ballistic transport dominates the I-V characteristics, whereas the effects of tunnelling cannot be neglected with the maximal value up to 0.8mA/mu m when the channel length of MOSFET scales down to 25 nm. The effects of tunnelling transport lower the threshold voltage V-t. The ballistic current based on fully 3-D quantum mechanical simulation is relatively large and has small on-off ratio compared with results derived from the calculation methods of Luo et al. |
| ISSN: 0256-307X |
| Article Number: 057101 |
| DOI: 10.1088/0256-307X/27/5/057101 |
| Record 9 of 16 |
| Author(s): Hou, QF (Hou Qi-Feng); Wang, XL (Wang Xiao-Liang); Xiao, HL (Xiao Hong-Ling); Wang, CM (Wang Cui-Mei); Yang, CB (Yang Cui-Bai); Li, JM (Li Jin-Min) |
| Title: Variation of Optical Quenching of Photoconductivity with Resistivity in Unintentional Doped GaN |
| Source: CHINESE PHYSICS LETTERS, 27 (5): Art. No. 057104 MAY 2010 |
| Abstract: The optical quenching of photoconductivity under dual illumination in GaN samples with different resistivity is investigated to reveal the variation of deep levels. The samples are grown by metal organic chemical vapour deposition without intentional doping. Quenching bands centered at 1.35 eV, 1.55 eV, 1.98 eV, and 2.60 eV are observed. It is found that the 1.98 eV quenching band is dominated in all the samples and the 2.60 eV band is observed only in the high-resistivity samples. The possible defect levels responsible for the quenching bands and the origin of different quenching behaviour at 2.60 eV are discussed. It is suggested that the defect level responsible for quenching at 2.60 eV plays an important role for the enhancement of resistivity. |
| ISSN: 0256-307X |
| Article Number: 057104 |
| DOI: 10.1088/0256-307X/27/5/057104 |
| Record 10 of 16 |
| Author(s): Peng, YC (Peng Ying-Cai); Fan, ZD (Fan Zhi-Dong); Bai, ZH (Bai Zhen-Hua); Zhao, XW (Zhao Xin-Wei); Lou, JZ (Lou Jian-Zhong); Cheng, X (Cheng Xu) |
| Title: Blue Luminescent Properties of Silicon Nanowires Grown by a Solid-Liquid-Solid Method |
| Source: CHINESE PHYSICS LETTERS, 27 (5): Art. No. 057305 MAY 2010 |
| Abstract: Silicon nanowires (SiNWs) were grown directly from n-(111) single-crystal silicon (c-Si) substrate based on a solid-liquid-solid mechanism, and Au film was used as a metallic catalyst. The room temperature photoluminescence properties of SiNWs were observed by an Xe lamp with an exciting wavelength of 350 nm. The results show that the SiNWs exhibit a strongly blue luminescent band in the wavelength range 400-480 nm at an emission peak position of 420 nm. The luminescent mechanism of SiNWs indicates that the blue luminescence is attributed to the oxygen-related defects, which are in SiOx amorphous oxide shells around the crystalline core of SiNWs. |
| ISSN: 0256-307X |
| Article Number: 057305 |
| DOI: 10.1088/0256-307X/27/5/057305 |
| Record 11 of 16 |
| Author(s): Guo, WH (Guo Wan-Hong); Liu, JQ (Liu Jun-Qi); Lu, QY (Lu Quan-Yong); Zhang, W (Zhang Wei); Li, L (Li Lu); Wang, LJ (Wang Li-Jun); Liu, FQ (Liu Feng-Qi); Wang, ZG (Wang Zhan-Guo) |
| Title: Design of surface emitting distributed feedback quantum cascade laser with single-lobe far-field pattern and high outcoupling efficiency |
| Source: CHINESE PHYSICS B, 19 (5): Art. No. 054208 MAY 2010 |
| Abstract: A 7.8-mu m surface emitting second-order distributed feedback quantum cascade laser (DFB QCL) structure with metallized surface grating is studied. The modal property of this structure is described by utilizing coupled-mode theory where the coupling coefficients are derived from exact Floquet-Bloch solutions of infinite periodic structure. Based on this theory, the influence of waveguide structure and grating topography as well as device length on the laser performance is numerically investigated. The optimized surface emitting second-order DFB QCL structure design exhibits a high surface outcoupling efficiency of 22% and a low threshold gain of 10 cm(-1). Using a pi phase-shift in the centre of the grating, a high-quality single-lobe far-field radiation pattern is obtained. |
| ISSN: 1674-1056 |
| Article Number: 054208 |
| DOI: 10.1088/1674-1056/19/5/054208 |
| Record 12 of 16 |
| Author(s): Zhao, DG (Zhao De-Gang); Zhang, S (Zhang Shuang); Liu, WB (Liu Wen-Bao); Hao, XP (Hao Xiao-Peng); Jiang, DS (Jiang De-Sheng); Zhu, JJ (Zhu Jian-Jun); Liu, ZS (Liu Zong-Shun); Wang, H (Wang Hui); Zhang, SM (Zhang Shu-Ming); Yang, H (Yang Hui); Wei, L (Wei Long) |
| Title: Role of Ga vacancies in enhancing the leakage current of GaN Schottky barrier ultraviolet photodetectors |
| Source: CHINESE PHYSICS B, 19 (5): Art. No. 057802 MAY 2010 |
| Abstract: The leakage current of GaN Schottky barrier ultraviolet photodetectors is investigated. It is found that the photodetectors adopting undoped GaN instead of lightly Si-doped GaN as an active layer show a much lower leakage current even when they have a higher dislocation density. It is also found that the density of Ga vacancies in undoped GaN is much lower than in Si-doped GaN. The Ga vacancies may enhance tunneling and reduce effective Schottky barrier height, leading to an increase of leakage current. It suggests that when undoped GaN is used as the active layer, it is necessary to reduce the leakage current of GaN Schottky barrier ultraviolet photodetector. |
| ISSN: 1674-1056 |
| Article Number: 057802 |
| DOI: 10.1088/1674-1056/19/5/057802 |
| Record 13 of 16 |
| Author(s): Wu, WJ (Wu Wen-jin); Wang, HW (Wang Hong-wu); Chen, SJ (Chen Shao-jiang); Guo, TT (Guo Ting-ting); Wang, SJ (Wang Shou-jue); Su, Q (Su Qian); Sun, M (Sun Ming); An, D (An Dong) |
| Title: Fast Discrimination of Commerical Corn Varieties Based on Near Infrared Spectra |
| Source: SPECTROSCOPY AND SPECTRAL ANALYSIS, 30 (5): 1248-1251 MAY 2010 |
| Abstract: The existing methods for the discrimination of varieties of commodity corn seed are unable to process batch data and speed up identification, and very time consuming and costly. The present paper developed a new approach to the fast discrimination of varieties of commodity corn by means of near infrared spectral data. Firstly, the experiment obtained spectral data of 37 varieties of commodity corn seed with the Fourier transform near infrared spectrometer in the wavenurnber range from 4 000 to 12 000 cm (1). Secondly, the original data were pretreated using statistics method of normalization in order to eliminate noise and improve the efficiency of models. Thirdly, a new way based on sample standard deviation was used to select the characteristic spectral regions, and it can search very different wavenumbers among all wavenumbers and reduce the amount of data in part. Fourthly, principal component analysis (PCA) was used to compress spectral data into several variables, and the cumulate reliabilities of the first ten components were more than 99.98%. Finally, according to the first ten components, recognition models were established based on BPR. For every 25 samples in each variety, 15 samples were randomly selected as the training set. The remaining 10 samples of the same variety were used as the first testing set, and all the 900 samples of the other varieties were used as the second testing set. Calculation results showed that the average correctness recognition rate of the 37 varieties of corn seed was 94.3%. Testing results indicate that the discrimination method had higher precision than the discrimination of various kinds of commodity corn seed. In short, it is feasible to discriminate various varieties of commodity corn seed based on near infrared spectroscopy and BPR. |
| ISSN: 1000-0593 |
| DOI: 10.3964/j.issn.1000-0593(2010)05-1248-04 |
| Record 14 of 16 |
| Author(s): Wang, SQ (Wang, Shaoqin); Zhou, LL (Zhou, Liling); Zeng, ZY (Zeng, Zhao Yang) |
| Title: Interference in transport through double barriers in interacting quantum wires |
| Source: PHYSICAL REVIEW B, 81 (15): Art. No. 155438 APR 15 2010 |
| Abstract: We investigate interference effects of the backscattering current through a double-barrier structure in an interacting quantum wire attached to noninteracting leads. Depending on the interaction strength and the location of the barriers, the backscattering current exhibits different oscillation and scaling characteristics with the applied voltage in the strong and weak interaction cases. However, in both cases, the oscillation behaviors of the backscattering current are mainly determined by the quantum mechanical interference due to the existence of the double barriers. |
| ISSN: 1098-0121 |
| Article Number: 155438 |
| DOI: 10.1103/PhysRevB.81.155438 |
| Record 15 of 16 |
| Author(s): Lv, XQ (Lv, X. Q.); Jin, P (Jin, P.); Wang, WY (Wang, W. Y.); Wang, ZG (Wang, Z. G.) |
| Title: Broadband external cavity tunable quantum dot lasers with low injection current density |
| Source: OPTICS EXPRESS, 18 (9): 8916-8922 APR 26 2010 |
| Abstract: Broadband grating-coupled external cavity laser, based on InAs/GaAs quantum dots, is achieved. The device has a wavelength tuning range from 1141.6 nm to 1251.7 nm under a low continuous-wave injection current density (458 A/cm(2)). The tunable bandwidth covers consecutively the light emissions from both the ground state and the 1st excited state of quantum dots. The effects of cavity length and antireflection facet coating on device performance are studied. It is shown that antireflection facet coating expands the tuning bandwidth up to similar to 150 nm, accompanied by an evident increase in threshold current density, which is attributed to the reduced interaction between the light field and the quantum dots in the active region of the device. (C) 2010 Optical Society of America |
| ISSN: 1094-4087 |
| Record 16 of 16 |
| Author(s): Cao, YL (Cao, Yu-Lian); Yang, T (Yang, Tao); Xu, PF (Xu, Peng-Fei); Ji, HM (Ji, Hai-Ming); Gu, YX (Gu, Yong-Xian); Wang, XD (Wang, Xiao-Dong); Wang, Q (Wang, Qing); Ma, WQ (Ma, Wen-Quan); Chen, LH (Chen, Liang-Hui) |
| Title: Delay of the excited state lasing of 1310 nm InAs/GaAs quantum dot lasers by facet coating |
| Source: APPLIED PHYSICS LETTERS, 96 (17): Art. No. 171101 APR 26 2010 |
| Abstract: In this letter, we present a facet coating design to delay the excited state (ES) lasing for 1310 nm InAs/GaAs quantum dot lasers. The key point of our design is to ensure that the mirror loss of ES is larger than that of the ground state by decreasing the reflectivity of the ES. In the facet coating design, the central wavelength is at 1480 nm, and the high- and low-index materials are Ta2O5 and SiO2, respectively. Compared with the traditional Si/SiO2 facet coating with a central wavelength of 1310 nm, we have found that with the optimal design the turning temperature of the ES lasing has been delayed from 90 to 100 degrees C for the laser diodes with cavity length of 1.2 mm. Furthermore, the characteristic temperature (T-0) of the laser diodes is also improved. |
| ISSN: 0003-6951 |
| Article Number: 171101 |
| DOI: 10.1063/1.3418647 |
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