Current Issue : July - September Volume : 2019 Issue Number : 3 Articles : 5 Articles
An ever-growing market demand for board (second) level packages (e.g., embedded\nsystems, system-on-a-chip, etc.) poses newer challenges for its manufacturing industry in terms\nof competitive pricing, higher reliability, and overall dimensions. Such packages are encapsulated\nfor various reasons including thermal management, protection from environmental conditions\nand dust particles, and enhancing the mechanical stability. In the due course of reducing overall\nsizes and material saving, an encapsulation as thin as possible imposes its own significance.\nSuch a thin-walled conformal encapsulation serves as an added advantage by reducing the\nthermo-mechanical stresses occurring due to thermal-cyclic loading, compared to block-sized or\nthicker encapsulations. This paper assesses the encapsulation process of a board-level package\nby means of thermoset injection molding. Various aspects reviewed in this paper include the\nconception of a demonstrator, investigation of the flow simulation of the injection molding process,\nexecution of molding trials with different encapsulation thicknesses, and characterization of the\npackages. The process shows a high dependence on the substrate properties, injection molding\nprocess parameters, device mounting tolerances, and device geometry tolerances. Nevertheless,\nthe thermoset injection molding process is suitable for the encapsulation of board-level packages\nlimiting itself only with respect to the thickness of the encapsulation material, which depends on\nother external aforementioned factors....
Stable luminance properties are essential for light-emitting devices with excellent performance. Thermal photoluminescence (PL)\nquenching of quantum dots (QDs) under a high temperature resulting from a surface hole or electron traps will lead to unstable and\ndim brightness. After treating CdZnSe/ZnSe QDs with TBP, which is a well-known passivation reagent of the anions, the excess Se\nsites on the surface of the QDs were removed and their PL quantum yields (QYs) was improved remarkable. Furthermore, after\nTBP treatment, the CdZnSe/ZnSe QDs exhibit no quenching phenomena even at a high temperature of 310 Degree Celcius. The\nelectroluminescent light-mitting diodes based on the QDs with TBP treatment also demonstrated satisfied performance with a\nmaximum current density of 1679.6 mA/cm2, a peak luminance of 89500 cd/m2, and the maximum values of EQE and\nluminescence efficiency are 15% and 14.9 cd/A, respectively. The performance of the fabricated devices can be further improved\nproviding much more in-depth studies on the CdZnSe/ZnSe QDs....
Emerging optical technology capable of addressing the limits in modern electronics must\nincorporate unique solutions to bring about a revolution in high-speed, on-chip data communication\nand information processing. Among the possible optical devices that can be developed, the\nelectrically driven, ultrasmall semiconductor light source is the most essential element for a compact,\npower-efficient photonic integrated circuit. In this review, we cover the recent development of the\nelectrically driven light-emitting devices based on various micro- and nano-scale semiconductor\noptical cavities. We also discuss the recent advances in the integration of these light sources with\npassive photonic circuits....
A patterned double-layer indium-tin oxide (ITO), including the first unpatterned ITO\nlayer serving as current spreading and the second patterned ITO layer serving as light extracting,\nwas applied to obtain uniform current spreading and high light extraction efficiency (LEE)\nof GaN-based ultraviolet (UV) light-emitting diodes (LEDs). Periodic pinhole patterns were formed\non the second ITO layer by laser direct writing to increase the LEE of UV LED. Effects of interval of\npinhole patterns on optical and electrical properties of UV LED with patterned double-layer ITO\nwere studied by numerical simulations and experimental investigations. Due to scattering out of\nwaveguided light trapped inside the GaN film, LEE of UV LED with patterned double-layer ITO\nwas improved as compared to UV LED with planar double-layer ITO. As interval of pinhole patterns\ndecreased, the light output power (LOP) of UV LED with patterned double-layer ITO increased.\nIn addition, UV LED with patterned double-layer ITO exhibited a slight degradation of current\nspreading as compared to the UV LED with a planar double-layer ITO. The forward voltage of UV\nLED with patterned double-layer ITO increased as the interval of pinhole patterns decreased....
The ultra-short pulsed laser annealing process enhances the performance of MoS2 thin film\ntransistors (TFTs) without thermal damage on plastic substrates. However, there has been insufficient\ninvestigation into how much improvement can be brought about by the laser process. In this paper,\nwe observed how the parameters of TFTs, i.e., mobility, subthreshold swing, Ion/Ioff ratio, and Vth,\nchanged as the the TFTsâ?? contacts were (1) not annealed, (2) annealed on one side, or (3) annealed on both\nsides. The results showed that the linear effective mobility increased from 13.14 [cm2/Vs]\n(not annealed) to 18.84 (one side annealed) to 24.91 (both sides annealed). Also, Ion/Ioff ratio increased\nfrom 2.27 * 105 (not annealed) to 3.14 * 105 (one side annealed) to 4.81 * 105 (both sides annealed),\nwith Vth shifting to negative direction. Analyzing the main reason for the improvement through the\nY function method (YFM), we found that both the contact resistance (Rc) and the channel interface\nresistance (Rch) improves after the pulsed laser annealings under different conditions. Moreover,\nthe Rc enhances more dramatically than the Rch does. In conclusion, our picosecond laser annealing\nimproves the performance of TFTs (especially, the Rc) in direct proportion to the number of annealings\napplied. The results will contribute to the investigation about correlations between the laser annealing\nprocess and the performance of devices....
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