Improved light extraction efficiency of AlGaN deep-ultraviolet light emitting diodes combining Ag-nanodots/Al reflective electrode with highly transparent p-type layer

Zhang, N; Xu, Fujun; Lang, Jing; Wang, L B; Wang, J M; Sun, Yong; Liu, B Y; Xie, Nan; Fang, Xuzhou; Yang, Xuelin; Kang, Xiaoning; Wang, X Q; Qin, Zhixin; Ge, Weikun; Shen, Bo

doi:10.1364/oe.416826

Cited by 22 publications

(6 citation statements)

References 26 publications

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“…4c. Then complex Ag nanodots/Al is adopted as the highly reflective p-electrode 30 , and 8 nm-thick p-GaN acts as the contact layer to ensure good Ohmic contact. DUV-LEDs show good rectifying behavior with a turn-on voltage of 6.2 V in the I-V curve as shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Sub-nanometer ultrathin epitaxy of AlGaN and its application in efficient doping

Wang

et al. 2022

Light Sci Appl

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Solving the doping asymmetry issue in wide-gap semiconductors is a key difficulty and long-standing challenge for device applications. Here, a desorption-tailoring strategy is proposed to juggle the carrier concentration and transport. Specific to the p-doping issue in Al-rich AlGaN, self-assembled p-AlGaN superlattices with an average Al composition of over 50% are prepared by adopting this approach. The hole concentration as high as 8.1 × 1018 cm−3 is thus realized at room temperature, which is attributed to the significant reduction of effective Mg activation energy to 17.5 meV through modulating the activating path, as well as the highlighted Mg surface-incorporation by an intentional interruption for desorption. More importantly, benefiting from the constant ultrathin barrier thickness of only three monolayers via this approach, vertical miniband transport of holes is verified in the p-AlGaN superlattices, greatly satisfying the demand of hole injection in device application. 280 nm deep-ultraviolet light-emitting diodes are then fabricated as a demo with the desorption-tailored Al-rich p-AlGaN superlattices, which exhibit a great improvement of the carrier injection efficiency and light extraction efficiency, thus leading to a 55.7% increase of the light output power. This study provides a solution for p-type doping of Al-rich AlGaN, and also sheds light on solving the doping asymmetry issue in general for wide-gap semiconductors.

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Section: Resultsmentioning

confidence: 99%

Sub-nanometer ultrathin epitaxy of AlGaN and its application in efficient doping

Wang

et al. 2022

Light Sci Appl

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“…Although substituting a transparent p-AlGaN layer for p-GaN as the contact layer can significantly reduce photon absorption, it inevitably leads to a dramatic increase in the operating voltage of DUV FCLEDs with a p-AlGaN contact layer [10,11]. To address the contradiction between photon absorption and poor conductivity in the p-GaN/p-AlGaN contact layer, the concept of a thin p-GaN contact layer has been proposed [12].…”

Section: Introductionmentioning

confidence: 99%

Enhanced efficiency of deep ultraviolet light-emitting diodes utilizing full-coverage Al reflector and highly reflective Ni/Rh p-electrode

Lv,

Liao,

Zhou

2024

Semicond. Sci. Technol.

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Increasing the reflection of p-side is an effective way to improve the optoelectronic performance of flip-chip light-emitting diodes (FCLEDs). Here, we propose a full-coverage Al reflector (FAR) and a highly reflective Ni/Rh p-electrode to enhance the performance of DUV FCLEDs. The physical mechanism for the impact of the FAR and Ni/Rh electrode on the light extraction efficiency (LEE) is discussed theoretically. Simulations demonstrate that the combination of the FAR and Ni/Rh electrode improves the LEEs of transverse electric- and transverse magnetic-polarized light by 13.62% and 27.08%, respectively. At an injection current of 100 mA, the fabricated DUV FCLEDs with FAR and Ni/Rh electrode exhibits an external quantum efficiency of 4.01% and a wall plugging efficiency of 3.01%, which are 17.19% and 16.67% higher than those of conventional DUV FCLEDs, respectively. These results support the promise of the FAR and Ni/Rh electrode for high-power DUV LED applications.

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“…To address this issue, reflectors have been utilized to reflect the downward light back into the sapphire and further enhance light extraction. Metallic reflectors and distributed Bragg reflectors (DBRs) have been widely utilized to improve light extraction efficiencies (LEEs) of FCLEDs [23][24][25][26]. Because of their high reflectivity in the visible light wavelength region, Ag and Al have been broadly employed as the metallic reflectors.…”

Section: Introductionmentioning

confidence: 99%

Effect of distributed Bragg reflectors on optoelectronic characteristics of GaN-based flip-chip light-emitting diodes

Sun,

Shi,

Cui

et al. 2024

Semicond. Sci. Technol.

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Distributed Bragg reflectors have been widely utilized in GaN-based flip-chip light-emitting diodes (FCLEDs) owing to their excellent reflection performance. Recently, wide reflected angle DBR (WRA-DBR) has been suggested to enhance the optical characteristics of GaN-based FCLEDs by incorporating multiple sub-DBRs with varying central wavelengths. However, the reflectivity of WRA-DBR decreases at large incident angle from 425 nm to 550 nm, which restricts further optical performance improvement of FCLEDs. Here, we demonstrate a quintuple-stack DBR comprised of five sub-DBRs. The quintuple-stack DBR possesses a high reflectivity (>97.5%) for incident angles below 50° within the blue and green light wavelength ranges. Compared to WRA-DBR, quintuple-stack DBR exhibits a higher reflectivity in wavelength range of 425 nm to 550 nm and thinner multilayer thicknesses. Furthermore, stronger electric field intensities exist in the top facet and sidewalls of FCLED with quintuple-stack DBR, revealing that quintuple-stack DBR is beneficial for enhancing the light extraction efficiency. As a result, the light output power of FCLED with quintuple-stack DBR is ~3% higher than that of FCLED with WRA-DBR at 750 mA.

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Improved light extraction efficiency of AlGaN deep-ultraviolet light emitting diodes combining Ag-nanodots/Al reflective electrode with highly transparent p-type layer

Cited by 22 publications

References 26 publications

Sub-nanometer ultrathin epitaxy of AlGaN and its application in efficient doping

Sub-nanometer ultrathin epitaxy of AlGaN and its application in efficient doping

Enhanced efficiency of deep ultraviolet light-emitting diodes utilizing full-coverage Al reflector and highly reflective Ni/Rh p-electrode

Effect of distributed Bragg reflectors on optoelectronic characteristics of GaN-based flip-chip light-emitting diodes

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