S. M. Wang

Shanghai Institute of Microsystem And Information Technology, Shanghai, Shanghai Shi, China

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Publications (124)222.9 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We report the first successful growth of InGaPBi single crystals on InP substrate with Bi concentration far beyond the doping level by gas source molecular beam epitaxy. The InGaPBi thin films reveal excellent surface and structural qualities, making it a promising new III–V compound family member for heterostructures. The strain can be tuned between tensile and compressive by adjusting Ga and Bi compositions. The maximum achieved Bi concentration is 2.2 ± 0.4% confirmed by Rutherford backscattering spectroscopy. Room temperature photoluminescence shows strong and broad light emission at energy levels much smaller than the InP bandgap.
    Semiconductor Science and Technology 09/2015; 30(9). DOI:10.1088/0268-1242/30/9/094006
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    ABSTRACT: We present a novel method to characterize the internal quantum efficiency and internal optical loss of semiconductor lasers. Its basic concept is studying the dependence of the external quantum efficiency on the mirror reflectivity. This method is very different from the conventional one, which focuses on the external quantum efficiency as a function of cavity length. Our method has great advantages, such as the capability of measuring the internal quantum efficiency and optical loss of a single laser diode, which is intrinsically impossible by the conventional method.
    IEEE Photonics Technology Letters 06/2015; 27(11):1169-1172. DOI:10.1109/LPT.2015.2413991
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    ABSTRACT: We report on the InAs quantum dot (QD) external cavity laser (ECL) using a digital mirror device (DMD) as the key component for wavelength tuning. The InAs QD laser diode was grown by gas source molecular-beam epitaxy, which had a broad gain profile. Single mode operation was achieved with the side mode suppression ratio of 21 dB when the optical feed back was provided by a mirror pattern consisting of 9 micromirrors. Moreover, two-color lasing was demonstrated with two laser lines having frequency difference in the THz range. The incorporation of DMD in the ECL enables great flexibility and many unique features, such as high tuning speed independent to the tuning step, two-color or multi-color lasing, and adjustable intensity for individual laser lines.
    Journal of Crystal Growth 03/2015; DOI:10.1016/j.jcrysgro.2015.03.011
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    ABSTRACT: A novel approach is demonstrated on the synthesis of hollow carbon nanospheres (HCNs) and their applications as color converter for white light-emitting diodes. HCNs were synthesized in a hydrothermal process using hexamethylenetetramine as precursor. The synthesis involves a template-less and one-step aqueous method for the first time, which enables the growth of HCNs with the temperature as low as 160 degrees C. HCNs solutions exhibit strong yellow-green emission under ultraviolet light excitation and possess typical excitation-dependent photoluminescence (PL) behavior as carbon nanoparticles. We also used a facile coating method to coat a blue LED with HCNs layer which plays a role as color-converted phosphor. The LED shows bright white light, and the spectrum involves two main components, one-from the blue LED chip centered at 455 nm and one from HCNs centered at 520 nm.
    Materials Letters 07/2014; 126:71–74. DOI:10.1016/j.matlet.2014.03.162
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    ABSTRACT: InPBi was predicted to be the most robust infrared optoelectronic material but also the most difficult to synthesize within In-VBi (V = P, As and Sb) 25 years ago. We report the first successful growth of InPBi single crystals with Bi concentration far beyond the doping level by gas source molecular beam epitaxy. The InPBi thin films reveal excellent surface, structural and optical qualities making it a promising new III-V compound family member for heterostructures. The Bi concentration is found to be 2.4 ± 0.4% with 94 ± 5% Bi atoms at substitutional sites. Optical absorption indicates a band gap of 1.23 eV at room temperature while photoluminescence shows unexpectedly strong and broad light emission at 1.4-2.7 μm which can't be explained by the existing theory.
    Scientific Reports 06/2014; 4:5449. DOI:10.1038/srep05449
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    ABSTRACT: We propose a novel semiconductor compatible path for nano-graphene synthesis using precursors containing C-Br bonding and liquid catalyst. The unique combination of CBr4 as precursor and Ga as catalyst leads to efficient C precipitation at a synthesis temperature of 200°C or lower. The non-wetting nature of liquid Ga on tested substrates limits nano-scale graphene to form on Ga droplets and substrate surfaces at low synthesis temperatures of T ≤ 450°C and at droplet/substrate interfaces by C diffusion via droplet edges when T ≥ 400°C. Good quality interface nano-graphene is demonstrated and the quality can be further improved by optimization of synthesis conditions and proper selection of substrate type and orientation. The proposed method provides a scalable and transfer-free route to synthesize graphene/semiconductor heterostructures, graphene quantum dots as well as patterned graphene nano-structures at a medium temperature range of 400-700°C suitable for most important elementary and compound semiconductors.
    Scientific Reports 04/2014; 4:4653. DOI:10.1038/srep04653
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    ABSTRACT: A theoretical investigation on explanation of the composition profile in triangular and hexagonal cross-sections of InGaN/GaN core–shell nanowires is presented by combining the finite elements method (FEM) and method of moving asymptotes (MMA) in the framework of thermodynamics. Our models can account for strain effect on indium composition. In both models, the maximum indium content through segregation arises either at the side length or at the corner of the InGaN shell. The simulated results are found in good agreement with those of experimental data, thus providing a good guidance for the growth of high indium concentration of InGaN/GaN core–shell nanowires.
    Solid State Communications 01/2014; 178:1–6. DOI:10.1016/j.ssc.2013.10.011
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    ABSTRACT: We report on the growth of InGaP metamorphic layer by gas source molecular-beam epitaxy. After optimization of the growth temperatures of the compositionally graded InGaP layer and the indium content in the top metamorphic InGaP layer, almost fully relaxed metamorphic layer was obtained with surface roughness of only about 2.17 nm. Strong photoluminescence signals were measured from both InGaAs quantum well and InAs quantum dots embedded in the metamorphic layer, indicating that the top metamorphic layer had low density of threading dislocations.
    Journal of Crystal Growth 09/2013; 378:141-144. DOI:10.1016/j.jcrysgro.2012.12.138
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    ABSTRACT: Photoluminescence (PL) measurements are performed on one GaSb/AlGaSb single-quantum-well (SQW) sample and two dilute-bismuth (Bi) GaSb/AlGaSb SQW samples grown at 360 and 380 °C, at low temperatures and under magnetic fields. Bimodal PL features are identified in the dilute-Bi samples, and to be accompanied by abnormal PL blueshift in the sample grown at 360 °C. The bimodal PL features are found to be from similar origins of band-to-band transition by magneto-PL evolution. Analysis indicates that the phenomenon can be well interpreted by the joint effect of interfacial large-lateral-scale islands and Al/Ga interdiffusion due to Bi incorporation. The interdiffusion introduces about 1-monolayer shrinkage to the effective quantum-well thickness, which is similar to the interfacial islands height, and the both together result in an unusual shallow-terrace-like interface between GaSbBi and AlGaSb. A phenomenological model is established, the Bi content of isoelectronic incorporation and the exciton reduced effective mass are estimated for the GaSbBi sample grown at 380 °C, and a value of about 21 meV/% is suggested for the bandgap bowing rate of GaSbBi. An effective routine is suggested for determining the Bi content and the depth of the shallow-terraces at interface in dilute-Bi SQW structures.
    Journal of Applied Physics 04/2013; 113(15-15):153505-153507. DOI:10.1063/1.4801530
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    ABSTRACT: A first-principles study has been performed to evaluate the electronic structure and thermoelectric properties of Bi-2(Te1-xSex)(3) compound. The transport coefficients are then calculated within the semiclassical Boltzmann theory, and further evaluated as a function of chemical potential assuming a constant relaxation time and an averaged thermal conductivity. Our theoretical calculations show that the ZT value is 1.43 for Bi-2(Te1-xSex)(3) system, and it agrees well with previous experimental data. Crown Copyright
    Solid State Communications 02/2013; 155:34–39. DOI:10.1016/j.ssc.2012.10.037
  • 17th European Molecular Beam Epitaxy Workshop, Levi, Finland; 01/2013
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    ABSTRACT: In this paper, we report recent progresses on growth of dilute nitrides and 1.3 µm lasers on GaAs using molecular beam epitaxy at Chalmers University of Technology, Sweden. Intense long wavelength light emission up to 1.71 µm at room temperature has been achieved by using the N irradiation method and the low growth rate. It is also demonstrated that incorporation of N in relaxed InGaAs buffer grown on GaAs strongly enhances the optical quality of metamorphic InGaAs quantum wells. With the optimized growth conditions and the laser structures, we demonstrate 1.3 µm GaInNAs edge emitting lasers on GaAs with state-of-the-art performances including a low threshold current density, a high-characteristic temperature, a 3 dB bandwidth of 17 GHz and uncooled operation at 10 Gbit/s up to 110 °C. The laser performances are comparable with the best reported data from the InGaAsP lasers on InP and is superior to the InAs quantum dot lasers on GaAs.
    physica status solidi (b) 05/2011; 248(5):1207 - 1211. DOI:10.1002/pssb.201000788
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    ABSTRACT: The optical properties of GaInNAs quantum wells (QW) grown by molecular beam epitaxy with and without N-irradiation (i.e. grown by the classical method) were investigated by the contactless electroreflectance (CER), temperature-dependent photoluminescence (PL) and time-resolved PL (TRPL). From CER measurements it was concluded that one type of nitrogen nearest-neighbor environment (In-rich environment) is dominant for GaInNAs QWs grown with N-irradiation whereas various nitrogen environments are present for the reference GaInNAs QW (i.e. the sample obtained by the classical method). PL and TRPL measurements clearly show that the optical properties of GaInNAs QWs are affected mainly by the amount of the incorporated nitride atoms. It was observed that the PL decay time decreased from ~200 to ~40 ps when the nitrogen concentration is increased from 0.8 to 2.2%. In addition, the presence of As flux during N-irradiation reduces the amount of the incorporated nitrogen and simultaneously improves the optical quality of GaInNAs QWs (i.e. it weakens the carrier localization at low temperatures and improves the quantum efficiency of PL).
    Semiconductor Science and Technology 04/2011; 26(4). DOI:10.1088/0268-1242/26/4/045012
  • 16th European Molecular Beam Epitaxy Workshop, Alpe d’Huez, France; 01/2011
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    ABSTRACT: We present a novel computational method by combining the finite element method and the method of moving asymptotes to study the dislocation-induced composition profile in alloy semiconductors. Segregated cylindrical nanoscale regions appear around the dislocation core. We find that the dominant driving force of non-uniform composition is strain contribution. Moreover, the method can be applied to the dislocated nanoscale heterostructures which are inaccessible by atomic treatment.
    Solid State Communications 08/2010; 150(29-30):1275-1278. DOI:10.1016/j.ssc.2010.05.023
  • Y X Song, S M Wang, Z H Lai, M Sadeghi
    16th International Conference on Molecular Beam Epitaxy, Berlin, Germany; 01/2010
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    ABSTRACT: The degradation of 1.3 μ m GaInNAs lasers was investigated using accelerated aging tests. This was followed by comprehensive characterization, including standard light-current-voltage (L-I-V) characterization, capacitance measurements, photoluminescence microscopy (PLM), on-axis amplified spontaneous emission (ASE) spectra measurements, and photocurrent (PC) and electroluminescence (EL) spectroscopies. The slope efficiency of the device dropped by 50% with a 300% increase in the threshold current after the accelerated aging test. The ideality factors of the aged devices are higher than those of the unaged devices. PLM images showed no evidence of catastrophic optical mirror damage. The measured capacitances of the aged devices are all similar to those of the unaged devices, indicating that there was no significant dopant diffusion in the junction region. Fourier transforms of the ASE spectra showed that no intracavity defects were present in the aged lasers, suggesting that intracavity defects are not responsible for the rapid degradation of the aged devices. Although the PC measurements showed defects at 0.88–0.95 eV and at ∼0.76 eV , these defect signatures did not increase with aging. On the other hand, EL measurements revealed that radiative deep level defects were generated during the aging tests, which may be related to the degradation of the devices. Based on the above measurement results, we identify the generation of radiative deep level defects as the main causes of degradation of these devices.
    Journal of Applied Physics 12/2009; 106(9-106):093110 - 093110-7. DOI:10.1063/1.3256156
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    ABSTRACT: High-resolution x-ray diffraction (HRXRD) and photoreflectance (PR) spectroscopy were used to independently determine the In and N concentrations in GaInNAs alloys grown by solid-source molecular beam epitaxy (SSMBE). The lattice constant and bandgap energy can be expressed as two independent equations in terms of the In and N concentrations, respectively. The HRXRD measurement provided the lattice constant and the PR measurement extracted the bandgap energy. By simultaneously solving these two equations, we have determined the In and N concentrations with the error as small as 0.001.
    Semiconductor Science and Technology 09/2009; 24(10):105016. DOI:10.1088/0268-1242/24/10/105016
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    ABSTRACT: The emission wavelength of a GaInNAs quantum well (QW) laser was adjusted to 1310 nm, the zero dispersion wavelength of optical fibre, by an appropriate choice of QW composition and thickness and N concentration in the barriers. A triple QW design was employed to enable the use of a short cavity with a small photon lifetime while having sufficient differential gain for a large modulation bandwidth. High speed, ridge waveguide lasers fabricated from high quality material grown by molecular beam epitaxy exhibited a damped modulation response with a bandwidth of 13 GHz.
    Electronics Letters 04/2009; 45(7-45):356 - 357. DOI:10.1049/el.2009.3657
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    ABSTRACT: We present epitaxial growth of GaInNAs on GaAs by molecular beam epitaxy (MBE) using analog, digital and N irradiation methods. It is possible to realize GaInNAs quantum wells (QWs) with a maximum substitutional N concentration up to 6% and a strong light emission up to 1.71μm at 300K. High quality 1.3μm GaInNAs multiple QW edge emitting laser diodes have been demonstrated. The threshold current density (for a cavity of 100x1000μm2) is 300, 300, 400 and 940A/cm2 for single, double, triple and quadruple QW lasers, respectively. The maximum 3dB bandwidth reaches 17GHz and high-speed transmission at 10Gb/s up to 110°C under a constant voltage has been demonstrated.
    Microelectronics Journal 03/2009; 40(3):386-391. DOI:10.1016/j.mejo.2008.06.013

Publication Stats

808 Citations
222.90 Total Impact Points

Institutions

  • 2013–2014
    • Shanghai Institute of Microsystem And Information Technology
      Shanghai, Shanghai Shi, China
  • 1992–2014
    • Chalmers University of Technology
      • • Department of Microtechnology and Nanoscience
      • • Photonics Laboratory
      • • Department of Applied Physics
      Goeteborg, Västra Götaland, Sweden
  • 2007
    • University of Nottingham
      • Department of Electrical and Electronic Engineering
      Nottingham, ENG, United Kingdom