| 1. |
- Anderson, J. P., et al.
(författare)
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A nearby super-luminous supernova with a long pre-maximum plateau and strong C (II) features
- 2018
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 620
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Tidskriftsartikel (refereegranskat)abstract
- Context. Super-luminous supernovae (SLSNe) are rare events defined as being significantly more luminous than normal terminal stellar explosions. The source of the additional power needed to achieve such luminosities is still unclear. Discoveries in the local Universe (i.e. z < 0.1) are scarce, but afford dense multi-wavelength observations. Additional low-redshift objects are therefore extremely valuable.Aims. We present early-time observations of the type I SLSN ASASSN-18km/SN 2018bsz. These data are used to characterise the event and compare to literature SLSNe and spectral models. Host galaxy properties are also analysed.Methods. Optical and near-IR photometry and spectroscopy were analysed. Early-time ATLAS photometry was used to constrain the rising light curve. We identified a number of spectral features in optical-wavelength spectra and track their time evolution. Finally, we used archival host galaxy photometry together with H( II )region spectra to constrain the host environment.Results. ASASSN-18km/SN 2018bsz is found to be a type I SLSN in a galaxy at a redshift of 0.0267 (111 Mpc), making it the lowest-redshift event discovered to date. Strong C- II lines are identified in the spectra. Spectral models produced by exploding a Wolf-Rayet progenitor and injecting a magnetar power source are shown to be qualitatively similar to ASASSN-18km/SN 2018bsz, contrary to most SLSNe-I that display weak or non-existent C (II) lines. ASASSN-18km/SN 2018bsz displays along, slowly rising, red plateau of >26 days, before a steeper, faster rise to maximum. The host has an absolute magnitude of -19.8 mag (r), a mass of M-* = 1.5(-0.33)(+0.08) x 10(9) M-circle dot, and a star formation rate of =0.50(-0.19)(+2.22) M-circle dot yr(-1). A nearby H (II) region has an oxygen abundance (O3N2) of 8.31 +/- 0.01 dex.
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| 2. |
- Desmaris, Vincent, 1977, et al.
(författare)
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Influence of oxynitride (SiOxNy) passivation on the microwave performance of AlGaN/GaN HEMTs
- 2008
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Ingår i: Solid-State Electronics. ; 52, s. 632-636
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Tidskriftsartikel (refereegranskat)abstract
- The effects of the composition of oxynitride passivations (SiOxNy) deposited by plasma enhanced chemical-vapor deposition (PECVD) at room temperature on the microwave performance of AlGaN/GaN high electron mobility transistors (HEMTs) were investigated. Five different SiOxNy passivating layers were deposited covering the whole range of dielectrics combinations from SiOx to SiNy. Their impacts on the HEMT performance were studied by means of DC, S-parameters, pulsed IV and load-pull measurements. The oxynitride dielectric with a refraction index of 1.58 was shown to be an effective SiOxNy passivation for limiting the gate-lag effects in the HEMTs and at the same time increasing the breakdown voltage of the device. It is thus a promising passivation layer for microwave power high voltage and high power applications.
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| 3. |
- Hsu, L. H., et al.
(författare)
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Design and Fabrication of 0/1-Level RF-Via Interconnect for RF-MEMS Packaging Applications
- 2010
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Ingår i: IEEE Transactions on Advanced Packaging. - 1521-3323. ; 33:1, s. 30-36
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the parametric study of RF-via (0-level) and flip-chip bump (1-level) transitions for applications of packaging coplanar RF-MEMS devices. The key parameters were found to be the bumps' and vias' positions and the overlap of the metal pads, which should be carefully considered in the entire two levels of packages. The length of the backside transmission line, determining the MEMS substrate area, showed minor influence on the interconnect performance. With the experimental results, the design rules have been developed and established. The optimized interconnect structure for the two levels of packages demonstrates the return loss beyond 15 dB and the insertion loss within 0.6 dB from dc to 60 GHz.
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| 4. |
- Hsu, L. H., et al.
(författare)
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Design, Fabrication, and Reliability of Low-Cost Flip-Chip-On-Board Package for Commercial Applications up to 50 GHz
- 2012
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Ingår i: IEEE Transactions on Components, Packaging and Manufacturing Technology. - 2156-3985 .- 2156-3950. ; 2:3, s. 402-409
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a flip-chip-on-board (FCOB) packaging technology using a Rogers RO3210 laminate for microwave applications. Compared to the conventional microwave packaging architecture, the proposed FCOB technology skips one level of the ceramic package and thus results in lower reflections and manufacturing costs. To fulfill the small dimension requirement on printed circuit boards, the coplanar waveguide (CPW) transmission line and flip-chip bump were fabricated on a high-k RO3210 board (epsilon(r) = 10.2) with photolithography and electroplating. The GaAs chip patterned with the CPW line was then flip-chip-mounted onto the RO3210 laminate board. This structure displayed excellent performance from dc to 50 GHz with a return loss S-11 greater than 18 dB and insertion loss S-21 less than 0.5 dB. Meanwhile, the flip-chip bonding of the in-house-fabricated In0.52Al0.As-48/In0.6Ga0.4As metamorphic high-electron-mobility transistor devices on RO3210 also displayed excellent gain performance with a small degradation of 1 dB from dc to 40 GHz, showing the potential of implementing microwave integrated circuits on RO3210. To enhance the mechanical reliability, an epoxy-based underfill was injected into the flip-chip assemblies. Thermal cycling tests were performed to test the interconnect reliability, and the results indicated that the samples passed the thermal cycling test at least up to 600 cycles, showing excellent reliability for commercial applications. To the best of the authors' knowledge, this is the first study that evaluates the use of the RO3210 laminate for microwave flip-chip in open literature.
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| 5. |
- Hsu, Li-Han, 1981, et al.
(författare)
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Design of Flip-Chip Interconnect Using Epoxy-Based Underfill Up to V-Band Frequencies With Excellent Reliability
- 2010
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 58:8, s. 2244-2250
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This study demonstrates a flip-chip interconnect with epoxy-based underfill (epsilon(r) = 3.5 and tan delta = 0.02 at 10 MHz) for packaging applications up to V-band frequencies. To achieve the best interconnect performance, both the matching designs on GaAs chip and Al2O3 substrate were adopted with the underfill effects taken into consideration. The optimized flip-chip interconnect showed excellent performance from dc to 67 GHz with return loss below -20 dB and insertion loss less than 0.6 dB. Furthermore, the dielectric loss induced by the underfill was extracted from measurement and compared with the simulation results. The reliability tests including 85 degrees C/85 % relative humidity test, thermal cycling test, and shear force test were performed. For the first time, the S-parameters measurement was performed to check the flip-chip reliability, and no performance decay was observed after 1000 thermal cycles. Moreover, the mechanical strength was improved about 12 times after the underfill was applied. The results show that the proposed flip-chip architecture has excellent reliability and can be applied for commercial applications.
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| 6. |
- Hsu, Li-Han, 1981, et al.
(författare)
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Fabrication process and 110 GHz measurement result of MS-to-CPW RF-via transition for RF-MEMS devices packaging applications
- 2009
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Ingår i: 2009 International Conference on Compound Semiconductor Manufacturing Technology, CS MANTECH 2009. - 9781893580138
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Konferensbidrag (refereegranskat)abstract
- This paper presents the fabrication process of RF-via (0-level) and flip-chip bump (1-level) transitions for applications of packaging MS (microstrip) RF-MEMS devices. The interconnect structure with MS-to-CPW transition between GaAs MEMS substrate and Al2O3 motherboard was in-house fabricated. A novel fabrication process for RF-MEMS packaging is in detail. After fabrication, the samples were measured up to 110 GHz using on-wafer probing measurement. From the measured results, the insertion loss of entire interconnect structure is better than -2 dB up to 100 GHz, documenting the feasibility for millimeter-wave RF-MEMS devices packaging applications.
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| 7. |
- Hsu, Li-Han, 1981, et al.
(författare)
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Flip-chip assembled 7 GHz ultra-low phase-noise InGaP HBT oscillator
- 2010
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Ingår i: 2010 International Conference on Compound Semiconductor Manufacturing Technology; Portland, OR; United States; 17 May 2010 through 20 May 2010. - 9781893580152
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Konferensbidrag (refereegranskat)abstract
- This paper reports on a flip-chip assembled 7 GHz ultra-low phase-noise GaAs InGaP heterojunction bipolar transistor (HBT) monolithic microwave integrated circuit (MMIC) oscillator. The cross-coupled oscillator was flip-chip bonded to an in-house fabricated Al2O3 carrier with patterns optimized for low-loss transitions. After flip-chip, the phase noise of the crosscoupled InGaP HBT oscillator was improved due to an increased Q-factor of the resonant tank. An ultra-low phase-noise of -112 dBc/Hz @ 100 kHz offset and -128 dBc/Hz @ 1 MHz offset with a high output power of 7 dBm at 7 GHz was achieved. To our best knowledge, this is the lowest phase noise reported for a flip-chip assembled oscillator.
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| 8. |
- Hsu, Li-Han, 1981, et al.
(författare)
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Flip-Chip-Based Multichip Module for Low Phase-Noise V -Band Frequency Generation
- 2010
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 58:9, s. 2408-2419
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- This paper reports on a flip-chip (FC)-based multichip module (MCM) for low phase-noise (PN) V -band frequency generation. A high-performance x8 GaAs metamorphic high-electron mobility transistor monolithic microwave integrated circuit (MMIC) multiplier and a low PN 7-GHz GaAs InGaP heterojunction bipolar transistor (HBT) MMIC oscillator were used in the module. The microstrip MMICs were FC bonded to an Al2O3 carrier with patterns optimized for low-loss transitions. The FC-based module was experimentally characterized to have a PN of -88 dBe/Hz @ 100-kHz offset and -112 dBc/Hz @ 1-MHz offset with an output power of 11 dBm. For comparison, the MMICs were also FC bonded as individual chips and the performance was compared with the bare dies without FC bonding. It was verified that the FC bonding has no detrimental effect on the MMIC performance. The tests revealed that the FC module provided improved performance. To our best knowledge, this is the first FC-based module for millimeter-wave frequency generation. The module also presents one of the best PN reported for millimeter-wave frequency sources.
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| 9. |
- Shiu, J. Y., et al.
(författare)
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Electrical Characterization and Transmission Electron Microscopy Assessment of Isolation of AlGaN/GaN High Electron Mobility Transistors with Oxygen Ion Implantation
- 2010
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Ingår i: Japanese Journal of Applied Physics. - 1347-4065 .- 0021-4922. ; 49:2, s. Art. no. 021001-
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Tidskriftsartikel (refereegranskat)abstract
- A multienergy oxygen ion implantation process was demonstrated to be compatible with the processing of high-power microwave AlGaN/GaN high electron mobility transistors (HEMTs). A high sheet resistivity and thermally stable isolation were demonstrated. The microstructures of implanted and postannealed specimens were investigated by transmission electron microscopy (TEM). The dependences of the sheet resistivity and different postannealing temperatures were correlated with the defect clusters and microstructure of lattice stacking faults. After 300 degrees C annealing, the sheet resistivity was higher than 10(12) Omega/square, which was attributed to the severe defect interaction eliminating the trapping centers and reducing the leakage current. A maximum output power density of 5.3 W/mm at V-gs = -4 V and V-ds = 50 V at 3 GHz was demonstrated on lag-free HEMTs without field plates on sapphire substrate.
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| 10. |
- Wu, W.C., et al.
(författare)
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60 GHz broadband 0=1-level RF-via interconnect for RF-MEMS packaging
- 2007
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Ingår i: Electronics Letters. ; 43:22, Oct. 25
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Tidskriftsartikel (refereegranskat)abstract
- The RF-via interconnect structure from the 0- to the 1-level packagefor coplanar RF-MEMS devices packaging is evaluated. The 0=1-levelinterconnect structure was designed and optimised using the electromagneticsimulation tool. The structure was then successfully fabricatedand characterised up to 67 GHz. The measured and simulatedresults show good agreement, demonstrating DC-to-60 GHz broadbandinterconnect performance through the two levels package
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