Improved Light Output of AlGaInP-Based Micro-Light Emitting Diode Using Distributed Bragg Reflector

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We investigated the effect of the surface roughness of the differently plated printed circuit board (PCB) on the reliability of AlGaInP-based LED packages. The electroless-plated PCB exhibited smoother surface than the electrolytic-plated one. Maximum debonding forces depended on the aspect ratios of hillocks on the plated PCB and voids. Thermo-mechanical maximum stress increased with increasing roughness height. For LED packages with the electroless-plated PCB, thermal resistance (R th ) from junction to PCB was increased by 57.43 K W −1 after operation at 85 °C with 35 mA for 1000 h (reliability test), whereas for LED package with the electrolytic-plated PCB, R th from junction to PCB increased by 4.1 K/W. The temperatures of the chip areas of the electroless-plated and electrolytic-plated samples were 91.3 and 85.3 °C, respectively, after the reliability test. For the electroless-plated and electrolytic samples, the view angles along the X and Y axes were 144.43°and 142.87°, and 143.23°and 145.58°, respectively, after the reliability test. Unlike the electrolytic-plated samples, the electroless-plated samples experienced 4.8% drop in the lumen maintenance and delamination between the mold resin and PCB after operation under the 60 °C/90% relative humidity condition with 35 mA for 1000 h.

Section: Resultsmentioning

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Effect of the Surface Morphology of Plated Printed Circuit Board on the Reliability of LED Packages

Kim

Song

et al. 2020

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“…DBR and main emission peaks were observed approximately at 612 and 623 nm, respectively. 48 Figure 1b presents variation of the peak emission wavelength and full width half maximum (FWHM) of the EL spectra as a function of current density. It is shown that regardless of the chip size and contact schemes, all of the samples experience a negligible shift in the emission peaks although the current density is increased from 10 to 100 A cm −2 .…”

Section: Resultsmentioning

confidence: 99%

Effects of Current, Temperature, and Chip Size on the Performance of AlGaInP-Based Red Micro-Light-Emitting Diodes with Different Contact Schemes

Lee

Shim

et al. 2021

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We have investigated the performance of AlGaInP-based red micro-light-emitting diodes (micro-LEDs) with different n-type contact schemes as functions of current, ambient temperature, and chip size. The samples with AuGe/Ni/Au contact revealed wider full width at half maximum of electroluminescence than that with the Pd/Ge contact. All samples also exhibited broad peaks at wavelengths between ∼632 and ∼640 nm, whose intensity depended on the type of contact schemes and temperature. Regardless of the contact schemes, the 10 μm-size samples showed a larger temperature-dependent reduction in the output power at current density of <50 A cm −2 than the 100 μm-size ones. Above 100 A cm −2 , however, both samples showed similar temperature dependence. Irrespective of the contact schemes, the main peak of the 100-μm samples was red-shifted, whereas no red-shift was detected in the 10-μm samples. The third peak of the AuGe-based contact samples became more dominant at 700 A cm −2 than the main peak, whereas that of the PdGe contact samples became more dominant at 1000 A cm −2 . Based on the chip size, current, contact scheme, and temperature dependence, the performance degradation of the red micro-LEDs is described and discussed.

“…So far, a limited study of ohmic contacts to n-AlInP has been performed. 4,15,16 For instance, Hao et al, 15 assessing the electrical behaviour of Pd/Sibased contacts to n-Al 0.5 In 0.5 P layer (E g = 2.3 eV), reported a minimum contact resistivity of about 6 × 10 −6 Ω cm 2 and that the contact resistivity was somewhat degraded when annealed at 400 °C. Further, it is generally known that LED performance is seriously influenced by the surface features of semiconductor layers, 17,18 whose surfaces comprise many dangling bonds, contaminants, and impurities.…”

mentioning

confidence: 99%

Inhomogeneous Barrier Height Characteristics of n-Type AlInP for Red AlGaInP-Based Light-Emitting Diodes

Cha¹,

Lee²,

Sim³

et al. 2022

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For micro-light-emitting diode (LED)-based display applications, such as virtual reality and augmented reality, high-performance Ohmic contacts (namely, the improvement of current injection efficiency) is vital to the realization of high-efficiency micro-LEDs. The surface Fermi level pinning characteristics could be comprehended in terms of the relation between work function of metals (ΦM) and Schottky barrier height (SBH, ΦB). In this study, we have investigated the surface Fermi level pinning characteristics of (001) n-AlInP surfaces by employing Schottky diodes with different metals. With an increase in the temperature, ΦB increases linearly and ideality factors (n) decreases. This behavior is related to the barrier height inhomogeneity. Inhomogeneity-model-based ΦB is evaluated to be in the range of 0.86 – 1.30 eV, which is dependent on the metal work functions and are similar to those measured from capacitance-voltage relation. Further, The S-parameter, the relation between B and M (dB/dM), is 0.36. This is indicative of the partial pinning of the surface Fermi level at the surface states placed at 0.95 eV below the conduction band. Furthermore, it is also shown that (NH4)2S-passivation results in an increases the mean SBH and the S-parameter (e.g., 0.52).