A 3W High-Voltage Single-Chip Green Light-Emitting Diode with Multiple-Cells Network

A parallel and series network structure was introduced into the design of the high-voltage single-chip (HV-SC) light-emitting diode to inhibit the effect of current crowding and to improve the yield. Using such a design, a 6.6 x 5 mm(2) large area LED chip of 24 parallel stages was demonstrated with 3 W light output power (LOP) at the current of 500 mA. The forward voltage was measured to be 83 V with the same current injection, corresponding to 3.5 V for a single stage. The LED chip's average thermal resistance was identified to be 0.28 K/W by using infrared thermography analysis

Compatibility of AlN/SiNx Passivation With LPCVD-SiNx Gate Dielectric in GaN-Based MIS-HEMT

In this letter, we demonstrate an integrated process that illustrates the compatibility of AlN/SiNx passivation with high-performance (i.e. low leakage and high breakdown) low-pressure chemical vapor deposition (LPCVD) SiNx gate dielectric for GaN-based MIS-HEMT. It is shown that the AlN/SiNx passivation structure maintains its superior capability of suppressing the current collapse after enduring high temperature of 780 degrees C during the LPCVD-SiNx deposition. The AlN/SiNx passivation is shown to be significantly better than the LPCVD-SiNx passivation by delivering small dynamic R-ON degradation, especially under high drain bias switching with V-DS > 100 V

Dynamic Characterizations of AlGaN/GaN HEMTs With Field Plates Using a Double-Gate Structure

 Anovel double-gate AlGaN/GaN HEMT, in which an additional top-gate covers the adjacent regions of a normal gate, was proposed and fabricated for the first time to compare the dynamic characteristics of AlGaN/GaN HEMTs with a source field plate (SFP) and a gate field plate (GFP). During the dynamic characterization, the device was configured in two operation modes: One is the SFP mode with the top gate biased at 0 V, and the other is the GFP mode applying the gate pulse signal on the top gate at the same time. Compared with an AlGaN/GaN HEMT without field plates, both GFP and SFP much improve the dynamic performances. Compared with the SFP, the GFP shows better dynamic performances with a similar to 34% reduction of switch-on delay time and similar to 6% reduction of dynamic ON-state resistance. Studying the dynamic characteristics and applying negative voltage on the top gate during the OFF state, the mechanism differences between the GFP and the SFP are discussed in detail

Fabrication of Large-Area Suspended MEMS Structures Using GaN-on-Si Platform

In this letter, piezosensitive elements featuring large-size suspended gallium nitride (GaN) microstructures are fabricated with a two-step dry-release technique using the GaN-on-Si platform. The suspended microstructures are integrated with highly piezosensitive AlGaN/GaN heterostructures as sensing units to realize the GaN-based integrated microsensors. To characterize the residual-stress distribution of the fabricated microstructures, micro-Raman spectroscopy is employed. A microaccelerometer structure with a 250 x 250-mu m(2) proof-mass area is fabricated with the proposed fabrication technique, and the piezoresponse properties of the integrated sensing elements are characterized through bending experiment

Wafer-Level Light Emitting Diode (WL-LED) Chip Simplified Package for Very-High Power Solid-State Lighting (SSL) Source

A simplified packaging process was successfully developed for a wafer-level light emitting diode (WL-LED) chip aiming at very-high power solid-state lighting (SSL) applications. Compared with the traditional chip-on-board (COB) technology, WL-LED chip not only greatly simplifies the packaging process but also enables the lighting source more compact. The fabricated blue WL-LED SSL source with a record-high light output power of 305 W exhibits similar to 30% wall plug efficiency at an input electrical power of 1026 W

Analysis of surface roughness in Ti/Al/Ni/Au Ohmic contact to AlGaN/GaN high electron mobility transistors

A mechanism of the formation of the bulges on the surface of Ti/Al/Ni/Au Ohmic contact in AlGaN/GaN high electron mobility transistors is proposed. According to the analysis of TEM images and corresponding electron dispersive x-ray spectra, the bulges were found to consist of Ni-Al alloy in the body and Au-Al alloy surrounding. We deduce that the bulges were formed due to Ni-Al alloy aggregation in some local areas during the rapid thermal annealing process, which accounts for the rough surface morphology

LASER-SCANNING MICROAREA PHOTOVOLTAGE IMAGING OF CORROSION ON THE SURFACE OF COPPER

The laser scanning micro-area photovoltage technique has been used in the research of copper corrosion in 3%NaCl solution. With the result of this method, the procedure of the local corrosion can be described, and the effect of the corrosion inhibitor can also be evaluated

5.3A/400V normally-off AlGaN/GaN-on-Si MOS-HEMT with high threshold voltage and large gate swing

<p> <span style="text-transform: none; background-color: rgb(255,255,255); text-indent: 0px; display: inline !important; font: 15px/24px Arial, sans-serif; white-space: normal; float: none; letter-spacing: normal; color: rgb(51,51,51); word-spacing: 0px; font-size-adjust: none; font-stretch: normal; -webkit-text-stroke-width: 0px"><font color="#333333"><font color="#333333">&nbsp;Normally-off AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) on Si substrate were fabricated with the fluorine-based treatment technique. By employing a 20nm-thick Al2O3 gate dielectric deposited by atomic layer deposition, the fabricated MOS-HEMT exhibits a large positive threshold voltage of +3.5V, a maximum gate input voltage of 15V, a maximum saturate drain current of 5.3A and an off-state breakdown voltage of 402V. The high threshold voltage and the large input voltage swing is expected to improve the electromagnetic interference immunity and safety of AlGaN/GaN MOS-HEMT power switches. </font></font></span></p

Analysis on the new mechanisms of low resistance stacked Ti/Al Ohmic contact structure on AlGaN/GaN HEMTs

A novel stacked Ti/Al based Ti/Al/Ti/Al/Ti/Al/Ti/Al/Ni/Au Ohmic contact structure is optimized. Compared with the conventional alloyed Ti/Al/Ni/Au Ohmic contact structure, the novel Ohmic contact structure can obtain much lower contact resistance and specific contact resistivity. Through analysis of x-ray diffraction spectra, cross-section transmission electron microscopy images and corresponding electron dispersive x-ray spectroscopy spectra in the novel stacked Ti/Al based Ohmic structure, the reactions between metals and the AlGaN layer were proven to be stable, uniform and continuous, which produced smooth contact interface. In addition, the top Au layer was prevented from diffusing downwards to the metal/AlGaN interface, which degraded the Ohmic performance

Plasmonic terahertz modulator based on a grating-coupled two-dimensional electron system

Electrically driven broadband modulator with large modulation depth and high speed is in high demand to meet the technical advancing and applications in terahertz fields recently. So far, the single-particle non-resonant absorption mechanism described by the Drude conductivity has been utilized in most of the related researches but is still not efficient enough. Here we proposed and demonstrated a terahertz modulator based on the collective electron plasma excitations (plasmons) in a grating-coupled two-dimensional electron gas in GaN/AlGaN heterostructure. By switching between the resonant and non-resonant conditions of the 2D plasmon excitation enabled by applying proper gate biases, the transmission of terahertz electromagnetic waves can be efficiently manipulated. Taking advantage of its resonant characteristic combined with the strong electric field enhancement in the active region, we experimentally achieved a maximum intensity modulation depth of 93%, a 3 dB operation bandwidth of similar to 400 kHz, and a small required driving voltage amplitude of 2 V at a cryogenic temperature of 8.7 K. Owing to its excellent performances, this active plasmon-based terahertz modulator may offer some promising solutions in several fields of terahertz technology in the future. Published by AIP Publishing