In this paper, we introduced the advantages of Vertical Light emitting diode (VLED) on copper alloy with Si-wafer level
packaging technologies. The silicon-based packaging substrate starts with a <100> dou-ble-side polished p-type silicon
wafer, then anisotropic wet etching technology is done to construct the re-flector depression and micro through-holes on
the silicon substrate. The operating voltage, at a typical cur-rent of 350 milli-ampere (mA), is 3.2V. The operation voltage
is less than 3.7V under higher current driving conditions of 1A. The VLED chip on Si package has excellent heat
dissipation and can be operated at high currents up to 1A without efficiency degradation. The typical spatial radiation
pattern emits a uniform light lambertian distribution from -65° to 65° which can be easily fit for secondary optics. The
correlated color temperature (CCT) has only 5% variation for daylight and less than 2% variation for warm white, when
the junction temperature is increased from 25°C to 110°C, suggesting a stable CCT during operation for general lighting
application. Coupled with aspheric lens and micro lens array in a wafer level process, it has almost the same light
distribution intensity for special secondary optics lighting applications. In addition, the ul-tra-violet (UV) VLED,
featuring a silicon substrate and hard glass cover, manufactured by wafer level pack-aging emits high power UV
wavelengths appropriate for curing, currency, document verification, tanning, medical, and sterilization applications.
High power near-UV LEDs, with wavelengths from 365nm to 410nm, were realized with an external
quantum efficiency from 12% to 45% for 365nm and 410nm, resp.
We show that the vertical LED design, coupled with the Silicon sub-mount package, gives very good
reliability that is suitable for many high power epoxy and polymer curing applications. UV LEDs are
proven to be a good replacement for high power mercury lamps currently used in the market.
GaN vertical LED on metal alloy substrate (VLEDMS) is a desirable technology suitable for solid state lighting
application from the viewpoint of reliability and lighting efficacy performance. A new top surface engineering technique
for efficient light extraction is employed to VLEDMS to improve power conversion efficiency further. Corrugated
pyramid shaped (CPS) surfaces are developed and formed on VLEDMS. By using such structure, VLEDMS exhibit a
great enhancement of around 20% in light output power, and a high efficiency of over 100 lumens per watt can also be
achieved by white LEDs. In the life test, the light output power of VLEDMS chips drop only by less than 10% within
3,000 hours, and the chips can also endure over 1000 cycles of thermal shocks without significant variations in electro-optical
performance. Therefore, the highly reliable and bright VLEDMS using CPS surface engineering technique is very
suitable for the solid-state lighting application.
GaN vertical LED on metal alloy substrate (VLEDMS) has been successfully realized for wavelength spectrum from near UV to green color. Owing to the vertical structure and highly heat-conductive metal alloy substrate, VLEDMS exhibits an ultra high brightness and excellent reliability suitable for solid state lighting (SSL) application. A brightness of 80Lm/W using 450 nm chip mixed with yellow phosphor was achieved by optimization of LED structure epitaxy, chip process and packaging. Using 405 nm chip with polychromatic phosphor a 50 Lm/W white light with color rendering index better than 90 was obtained. We also can get very good uniform correlated color temperature from package with VLEDMS chip.
In this paper we describe GaN based Vertical Light Emitting diode on Metal Alloy Substrate (VLEDMS) as a disruptive technology to solve the heat dissipation and current-crowding effect for the power device operated at high current. We focus on reliability features of VLEDMS under various operation regimes required for solid state lighting (SSL) application.
Vertical GaN based Light Emitting Diodes on metal alloy substrate were realized and characterized for solid state lighting application. An efficiency of more than 70 lumens/watt was achieved. In addition, these LEDs exhibit many advantages over those on sapphire under extreme operation conditions for general lighting application.
Large-area (1000×1000 μm2) p-side down InGaN light-emitting diodes (LEDs) have been fabricated by laser lift-off (LLO) technique. The p-side down LEDs with different geometric patterns of n-electrode were fabricated to investigate electrode pattern-dependent optical characteristics. Current crowding effect was first observed in in the p-side down InGaN LLO-LEDs. The LEDs with well designed n-electrode shows a uniform distribution of light-emitting pattern and higher out put power due to uniform current spreading and minimization of thermal effect. The output power saturation induced by current crowding in the LEDs with simplest geometric n-electrode was demonstrated. In absent of transparent contact layer for current spreading, the n-electrode pattern has remarkable influence on the current distribution and consequently the light output power of the large-area p-side down LEDs.
We report the results of the investigation of the structural, surface morphological, and optical properties of GaN films grown by hydride vapor phase epitaxy. These films were grown on sapphire substrate with no intentional dopings. These as-grown GaN film samples with thickness ranging from 5.58 micrometers to 14.9 micrometers were investigated under room temperature conditions. The surface morphology of these films was investigated using an atomic force microscopy (AFM). The root mean square values of surface roughness range from 0.281 nm to 0.133 nm. The thicker films show lower defect counts with defect density of about 2 X 108 cm-2. The structural property of these films was measured by double crystal x-ray diffraction. The full width at half maximum of x-ray diffraction angle decreases as the film thickness increases with a lowest FWHM of about 265.5 arcsec. The optical properties of these films were investigated by photoluminescence measurement at room temperature. The result show a dominant near band-edge UV emission peak that increases with the film thickness with very weak yellow emission band.
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