We have developed a normally-off GaN-based transistor using conductivity modulation, which we call a gate injection transistor (GIT). This new device principle utilizes hole-injection from the ...p-AlGaN to the AlGaN/GaN heterojunction, which simultaneously increases the electron density in the channel, resulting in a dramatic increase of the drain current owing to the conductivity modulation. The fabricated GIT exhibits a threshold voltage of 1.0 V with a maximum drain current of 200 mA/mm, in which a forward gate voltage of up to 6 V can be applied. The obtained specific ON-state resistance (R ON . A) and the OFF-state breakdown voltage (BV ds ) are 2.6 mOmega . cm 2 and 800 V, respectively. The developed GIT is advantageous for power switching applications.
A breakdown mechanism of polarized semiconductors represented by GaN-based materials is presented, based on the concept of a natural super junction, which is established by the inherent material ...polarization. In this concept, owing to the precise matching of positive and negative polarizations of both sides of GaN and AlGaN materials, average charge concentration in the material becomes nearly zero under reverse bias condition, which realizes extremely high breakdown voltage. This model is confirmed by device simulation taking all polarization charges of GaN-based materials into account. Furthermore, experimentally fabricated GaN-based Schottky barrier diodes showed a linear increase of breakdown voltage along the anode-cathode spacing, achieving a record breakdown voltage over 9000 V.
We have developed a high-power AlGaN/GaN HFET fabricated on 4-in conductive Si substrate with a source-via grounding (SVG) structure. The SVG structure enables efficient chip layout and high packing ...density by the vertical configuration. By establishing a high-quality epitaxial technology on a Si substrate and by significantly reducing the parasitic resistance, a very low specific on-state resistance of 1.9 m/spl Omega//spl middot/cm/sup 2/ is achieved. The breakdown voltage is as high as 350 V, which is attributed to the Si substrate acting as a backside field plate. Because of reduction of the parasitic inductance, very high level of current (2.0 kA/cm/sup 2/) transients, i.e., a turn-on time of 98 ps and a turn-off time of 96 ps, are successfully measured for the first time.
The data presented in this article are related to the research article entitled “Cyclic Shear behavior of conventional and harmonic structure-designed Ti-25Nb-25Zr β-titanium alloy: Back-stress ...hardening and twinning inhibition” (Dirras et al., 2017) 1. The datasheet describes the methods used to fabricate two β-titanium alloys having conventional microstructure and so-called harmonic structure (HS) design via a powder metallurgy route, namely the spark plasma sintering (SPS) route. The data show the as-processed unconsolidated powder microstructures as well as the post-SPS ones. The data illustrate the mechanical response under cyclic shear loading of consolidated alloy specimens. The data show how electron back scattering diffraction(EBSD) method is used to clearly identify induced deformation features in the case of the conventional alloy.
This letter describes an analysis of the degradation of InGaN-based laser diodes. The influence of current, temperature, and optical power level on the degradation kinetics has been analyzed by means ...of a wide set of stress tests carried out under different operating conditions. We demonstrate the following: 1.) the degradation rate is strongly related to the operating current level; 2.) high-temperature stress does not determine significant degradation of lasers characteristics; and 3.) the intensity of the optical field does not significantly influence the degradation rate. Degradation process is found to be electrothermally activated and is ascribed to the increase of the nonradiative recombination rate in the active layer, with subsequent decrease of the efficiency of the devices.
We demonstrate polarization control of vertical-cavity surface-emitting lasers (VCSELs) to any desired directions by utilizing surface plasmon resonance at a metal nanohole array. A silver nanohole ...array is integrated on the p-type distributed Bragg reflector of an 850-nm AlGaAs-GaAs-based VCSEL. The metal nanohole array placed at rectangular lattices with orthogonally different two periods, one of which meets the resonaint condition, exhibits strong polarization preference in optical transmission. Integrated four VCSELs with different directions of the rectangular arrays of nanoholes demonstrate successful control of the polarization angles. The VCSELs are closely located onto a one chip so that the optical outputs are easily coupled to one optical fiber. The presented VCSEL array will open a new horizon of multi-input multi-output communication systems by using polarization multiplexing.
This paper discusses the conception and development of a ball-on-plate balancing system based on mechatronic design principles. Realization of the design is achieved with the simultaneous ...consideration towards constraints like cost, performance, functionality, extendibility, and educational merit. A complete dynamic system investigation for the ball-on-plate system is presented in this paper. This includes hardware design, sensor and actuator selection, system modeling, parameter identification, controller design and experimental testing. The system was designed and built by students as part of the course
Mechatronics System Design at Rensselaer.
A high-power single-pole double throw (SPDT) switch IC using AlGaN/GaN heterojunction field-effect transistors (HFETs) is demonstrated for the first time. The reduction of on-resistance (R/sub on/) ...and off-capacitance (C/sub off/) for AlGaN/GaN HFETs enables the GaN-based switch IC that can be applied for practical RF applications. A novel Si-doping technique is employed to reduce ohmic contact resistance, which successfully reduces the R/sub on/. The C/sub off/ of the HFETs on a sapphire substrate is found to be smaller than that on a SiC substrate, together with low cost fabrication. The GaN-based SPDT switch IC with single-stage configuration is designed by using a circuit simulator based on the extracted device parameters. The fabricated SPDT switch IC achieves insertion loss of 0.26 dB and isolation of 27 dB at 1 GHz, as well as an extremely high-power handling capability of 43 W. This value is 10 times higher than that of typical GaAs-based switch ICs. In addition, the switch IC exhibits low distortion characteristics, where the third-order intercept point of 41 dBm is achieved. The chip size is reduced to 40% as compared with conventional four stage GaAs-based switch ICs by using the single-stage circuit configuration.
Spark plasma sintering was used to fabricate two Ti-25Zr-25Nb β-titanium alloys having a homogeneous microstructure and a so-called harmonic structure. Mechanical properties were evaluated by simple ...shear cyclic tests. The sample with homogeneous microstructure shows a large cumulative strain ~400% and a two-stage work-hardening associated with intense {332}〈113〉 mechanical twinning activity. Conversely, the harmonic-designed microstructure exhibits lesser cumulative strain ~200% but a higher cyclic strength. A complete twinning inhibition is observed. Indeed, the ultrafine-grained shell of the harmonic structure dispersed stress concentration. It accommodates plastic incompatibilities due to grain size difference by accumulating geometrically necessary dislocations at the shell/core vicinity.
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In this paper, we demonstrate a novel method to integrate photonic crystals (PhCs) on GaN-based blue light-emitting diodes (LEDs) using a silicon substrate as a mold for forming the PhCs. This method ...starts with fabricating a 2D grooved Si substrate as that mold. Subsequently, GaN-based epitaxial layers are grown on the Si mold-substrate, which effectively reduces the dislocation density in GaN by enhanced lateral epitaxial growth. After the epitaxial layers are bonded onto a highly reflective substrate, the Si mold-substrate is removed. This substrate-transfer technique replicates PhC from the mold-substrate on the LED surface free from processing damages. The resultant LEDs with PhC have outperformed the LEDs without PhC in the optical output power by 80%, taking advantage of the enhanced light extraction by PhC.
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