Invasive pneumococcal infection is the most common cause of HUS in Taiwan. Positive T-Ag activation and a direct Coombs' test are rapid predictors of SP-HUS in children with invasive pneumonia.

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This paper reports Al 0.27 Ga 0.73 N/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) with stacked Al 2 O 3 /HfO 2 gate dielectrics by using hydrogen peroxideoxidation/sputtering techniques. The Al 2 O 3 employed as a gate dielectric and surface passivation layer effectively suppresses the gate leakage current, improves RF drain current collapse and exhibits good thermal stability. Moreover, by stacking the good insulating high-k HfO 2 dielectric further suppresses the gate leakage, enhances the dielectric breakdown field and power-added efficiency, and decreases the equivalent oxide thickness. The present MOS-HEMT design has demonstrated superior improvements of 10.1% (16.4%) in the maximum drain-source current (I DS, max ), 11.4% (22.5%) in the gate voltage swing and 12.5%/14.4% (21.9%/22.3%) in the two-terminal gate-drain breakdown/turn-on voltages (BV GD /V ON ), and the present design also demonstrates the lowest gate leakage current and best thermal stability characteristics as compared to two reference MOS-HEMTs with a single Al 2 O 3 /(HfO 2 ) dielectric layer of the same physical thickness.

Novel Al 0.75 Ga 0.25 N/Al x Ga 1−x N/Al 0.75 Ga 0.25 N/AlN metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs) with symmetrically-graded widegap Al x Ga 1−x N channel (x = 0.75 → 0.25 → 0.75) grown on a SiC substrate are investigated. Al 2 O 3 was devised as the gate dielectric by using a non-vacuum ultrasonic spray pyrolysis deposition (USPD) technique. Device characteristics with respect to different etch depths of the source/drain recesses were studied. For a 2μm gate length (L G), the present widegap V-shape-channel MOS-HFET has shown improved maximum drain-source current density (I DS,max) of 299.3 A/mm at V DS = 20 V, I DS density at V GS = 0 V (I DSS0) of 153.9 mA/mm, on/off-current ratio (I on /I off) of 1.4 × 10 7 , extrinsic transconductance (g m,max) of 16.7 mS/mm, two-terminal off-state gate-drain breakdown voltage (BV GD) of −379 V, and three-terminal on-state drain-source breakdown voltage (BV DS) of 339 V. Besides, superior deep-UV sensing performance with high spectral responsivity (SR) of 1780 (810.2) A/W at wavelength λ = 250 (300) nm are also achieved. INDEX TERMS Al x Ga 1−x N, MOS-HFET, symmetrically-graded, widegap channel, Al 2 O 3 , non-vacuum ultrasonic spray pyrolysis deposition, spectral responsivity, deep-UV.

This work investigates temperature-dependent device characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) grown by a metal-organic chemical vapor deposition (MOCVD) system, and passivated by using hydrogen peroxide (H 2 O 2 ) oxidation method. The present oxide-passivated AlGaN/GaN HEMT can effectively improve device performances, including current drive, transconductance, gate-drain forward turn-on voltage (V on ), and gate-drain reverse breakdown voltage (BV GD ) at 300-480 K. In addition, improved RF and power performances have also been achieved as compared with an unpassivated device. The present oxide-passivated AlGaN/GaN HEMT is promising for high-temperature and high-power monolithic microwave integrated circuit (MMIC) applications.

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Improved electrical and deep-UV sensing characteristics of Al2O3-dielectric Al0.75Ga0.25N/n-AlxGa1−xN/Al0.75Ga0.25N/AlN metal-oxide-semiconductor hetero-structure field-effect transistors (MOS-HFETs), grown on a SiC substrate, with an AlGaN ultra-widegap channel design are investigated. 30 nm thick high-k Al2O3 was deposited as both the gate oxide and surface passivation layer by using a non-vacuum ultrasonic spray pyrolysis deposition (USPD) method. Improved device characteristics, including maximum drain-source current density (IDS,max) of 130.1 mA mm−1, maximum extrinsic transconductance (gm,max) of 11.8 mS mm−1, on/off-current ratio (Ion/Ioff) of 1.4 × 107, gate-voltage swing (GVS) linearity of 5.8 V, two-terminal off-state gate-drain breakdown voltage (BVGD) of −404 V, and three-terminal on-state drain-source breakdown voltage (BVDS) of 364 V at 300 K are obtained for the present MOS-HFET. The device has demonstrated high spectral responsivity (SR) of 737 A W−1 under 250 nm deep-UV radiation.

Al 0.22 Ga 0.78 As/In 0.24 Ga 0.76 As pseudomorphic high-electron-mobility transistors (pHEMTs) with metal-oxide-semiconductor (MOS)-gate structure or oxide passivation by using ozone water oxidation treatment have been comprehensively investigated. Annihilated surface states, enhanced gate insulating property and improved device gain have been achieved by the devised MOS-gate structure and oxide passivation. The present MOS-gated or oxide-passivated pHEMTs have demonstrated superior device performances, including superior breakdown, device gain, noise figure, high-frequency characteristics and power performance. Temperature-dependent device characteristics of the present designs at 300-450 K are also studied.