Improved Efficiency of Ultraviolet B Light‐Emitting Diodes with Optimized p‐Side

Kolbe, Tim; Knauer, A.; Raß, Jens; Cho, Hyun Kyong; Mogilatenko, A.; Hagedorn, Sylvia; Ploch, Neysha Lobo; Einfeldt, S.; Weyers, M.

doi:10.1002/pssa.202000406

Cited by 5 publications

(4 citation statements)

References 35 publications

(36 reference statements)

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“…The LED with good quality resulted in a low leakage current and low contact resistivity. Subsequently, this will reduce the forward voltage of the LED (Kolbe et al , 2020).…”

Section: Resultsmentioning

confidence: 99%

Effects of three-step magnesium doping in p-GaN layer on the properties of InGaN-based light-emitting diode

Hamzah

Ahmad

Asri

et al. 2021

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Purpose The purpose of this paper is to enhance the efficiency of the LED by introducing three-step magnesium (Mg) doping profile. Attention was paid to the effects of the Mg doping concentration of the first p-GaN layer (i.e. layer close to the active region). Attention was paid to the effects of the Mg doping concentration of the first p-GaN layer (i.e. layer close to the active region). Design/methodology/approach Indium gallium nitride (InGaN)–based light-emitting diode (LED) was grown on a 4-inch c-plane patterned sapphire substrate using metal organic chemical vapor deposition. The Cp2Mg flow rates for the second and third p-GaN layers were set at 50 sccm and 325 sccm, respectively. For the first p-GaN layer, the Cp2Mg flow rate varied from 150 sccm to 300 sccm to achieve different Mg dopant concentrations. Findings The full width at half maximum (FWHM) for the GaN (102) plane increases with increasing Cp2Mg flow rate. FWHM for the sample with 150, 250 and 300 sccm Cp2Mg flow rates was 233 arcsec, 236 arcsec and 245 arcsec, respectively. This result indicates that the edge and mixed dislocations in the p-GaN layer were increased with increasing Cp2Mg flow rate. Atomic force microscopy (AFM) results reveal that the sample grown with 300 sccm exhibits the highest surface roughness, followed by 150 sccm and 250 sccm. The surface roughness of these samples is 2.40 nm, 2.12 nm and 2.08 nm, respectively. Simultaneously, the photoluminescence (PL) spectrum of the 250 sccm sample shows the highest band edge intensity over the yellow band ratio compared to that of other samples. The light output power measurements found that the sample with 250 sccm exhibits high output power because of sufficient hole injection toward the active region. Originality/value Through this study, the three steps of the Mg profile on the p-GaN layer were proposed to show high-efficiency InGaN-based LED. The optimal Mg concentration was studied on the first p-GaN layer (i.e. layer close to active region) to improve the LED performance by varying the Cp2Mg flow rate. This finding was in line with the result of PL and AFM results when the samples with 250 sccm have the highest Mg acceptor and good surface quality of the p-GaN layer. It can be deduced that the first p-GaN layer doping has a significant effect on the crystalline quality, surface roughness and light emission properties of the LED epi structure.

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“…The LED with good quality resulted in a low leakage current and low contact resistivity. Subsequently, this will reduce the forward voltage of the LED (Kolbe et al , 2020).…”

Section: Resultsmentioning

confidence: 99%

Effects of three-step magnesium doping in p-GaN layer on the properties of InGaN-based light-emitting diode

Hamzah

Ahmad

Asri

et al. 2021

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“…AlGaN-based UVC and UVB LED heterostructures were grown on c-plane sapphire substrates by metal-organic vapor phase epitaxy [20,25]. The UVC LED heterostructure for emission at 265 nm was grown on a low defect density ELO AlN/sapphire template [26,27].…”

Section: Methodsmentioning

confidence: 99%

“…It consists of a 1 µm thick Al 0.76 Ga 0.24 N:Si current spreading layer, an Al 0.65 Ga 0.35 N:Si n-contact layer, an Al 0.63 Ga 0.37 N:Si/Al 0.48 Ga 0.52 N multiple quantum well (MQW), a 10 nm thick Al 0.85 Ga 0.15 N:Mg electron blocking heterostructure, and a 230 nm thick GaN:Mg p-contact layer. The UVB LED heterostructure for emission at 310 nm was grown on a planar AlGaN-AlN/sapphire template [25]. It consists of a 1.25 µm thick Al 0.55 Ga 0.45 N:Si current spreading layer, an In 0.015 Al 0.394 Ga 0.591 N:Si/In 0.015 Al 0.276 Ga 0.709 N MQW, a 15 nm Al 0.9 Ga 0.1 N:Mg electron blocking layer, a 100 nm Al 0.38 Ga 0.62 N:Mg cladding layer, and a 20 nm GaN:Mg p-contact layer.…”

Section: Methodsmentioning

confidence: 99%

Enhanced light extraction efficiency of UV LEDs by encapsulation with UV-transparent silicone resin

Wu¹,

Guttmann²,

Ploch³

et al. 2022

Semicond. Sci. Technol.

Self Cite

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Increase of light extraction efficiency (LEE) and total output power of UV LEDs emitting at 265 nm and 310 nm, respectively, after encapsulation with a UV-transparent silicone are studied. Raytracing simulations suggest that a properly placed hemispherical encapsulation with a refractive index in the range from 1.4 to 1.8 enhances the LEE from 8% to up to 16% for flip-chip mounted UV LEDs with non-reflective metal contacts. The simulations also show that the absorption coefficient of the encapsulant determines the maximum LEE and optimum dome diameter and that it should be below 3 cm-1. The silicone encapsulant exhibits a refractive index of 1.47 (1.45) and an absorption coefficient of 1.3 cm-1 (0.47 cm-1) at 265 nm (310 nm). AlGaN/sapphire-based UVC and UVB LED chips were flip-chip mounted on planar AlN ceramic packages and encapsulated with a 1.5 mm-radius hemispherical silicone dome. The total output power at an operation current of 350 mA increased from 27 mW to 46 mW for 265 nm LEDs and from 45 mW to 78 mW for 310 nm LEDs. This corresponds to an enhancement of about 70%, which agrees with the simulations. Moreover, far-field measurements of encapsulated LEDs showed a narrowing of the emission cone.

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“…The transparent conductive layer, the current spreading layer, current blocking layer [16][17][18] beneath the p-pad electrode and shapes diversity of electrode [19,20] are used extensively in the fabrication process of device. The short-period superlattice (SLs) [21] as the p-current spreading layers, n-type AlGaN/GaN/InGaN current spreading layer under multiple-quantum-wells (MQWs) active region [22], multi-layer stacked AlGaN/GaN structure [23] and n-GaN/p-GaN/n-GaN/p-GaN/n-GaN built-in junctions [24] in the n-GaN layer have been introduced in the InGaN/GaN LEDs to alleviate the current crowding effect. However, all these methods Crystals 2021, 11, 1203 2 of 7 have improved the current spreading, but also increase the complexity and uncontrollability of the experimental process to a certain extent.…”

Section: Introductionmentioning

confidence: 99%

Improved Performance of GaN-Based Ultraviolet LEDs with the Stair-like Si-Doping n-GaN Structure

Fan

Tao

et al. 2021

Crystals

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A method to improve the performance of ultraviolet light-emitting diodes (UV-LEDs) with stair-like Si-doping GaN layer is investigated. The high-resolution X-ray diffraction shows that the UV-LED with stair-like Si-doping GaN layer possesses better quality and a lower dislocation density. In addition, the experimental results demonstrate that light output power and wall plug efficiency of UV-LED with stair-like Si-doping GaN are significantly improved. Through the analysis of the experimental and simulation results, we can infer that there are two reasons for the improvement of photoelectric characteristics: reduction of dislocation density and alleviating of current crowding of UV-LEDs by introduced stair-like Si-doping GaN.

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Improved Efficiency of Ultraviolet B Light‐Emitting Diodes with Optimized p‐Side

Abstract: Figure 6. Electrical and optical characteristics of a flip-chip-mounted 310 nm LED measured under DC. Inset: the corresponding emission spectrum measured at 350 mA.

Cited by 5 publications

References 35 publications

Effects of three-step magnesium doping in p-GaN layer on the properties of InGaN-based light-emitting diode

Effects of three-step magnesium doping in p-GaN layer on the properties of InGaN-based light-emitting diode

Enhanced light extraction efficiency of UV LEDs by encapsulation with UV-transparent silicone resin

Improved Performance of GaN-Based Ultraviolet LEDs with the Stair-like Si-Doping n-GaN Structure

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