A Buried High<i>k</i>Insulator for Suppressing the Surface Recombination for GaN-Based Micro-Light-Emitting Diodes

Zhang, Muyao; Hang, Sheng; Chu, Chunshuang; Shao, Hua; Zhang, Yidan; Zhang, Yonghui; Zhang, Yandi; Zheng, Quan; Li, Qing; Zhang, Zi Hui

doi:10.1109/ted.2022.3164638

Cited by 10 publications

(8 citation statements)

References 22 publications

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“…For the former method, a better deposition method is required. Compared to PECVD, atomic layer deposition (ALD) is a better deposition method with higher resolution [ 8 – 10 , 22 – 25 ]. Due to the one-molecule-layer deposition per cycle process, ALD-passivated layers exhibit superior conformal coverage, resulting in more substantial suppression of surface recombination compared to PECVD-passivated layers.…”

Section: Resultsmentioning

confidence: 99%

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Efficiency improvement by using metal–insulator-semiconductor structure in InGaN/GaN micro-light-emitting diodes

Yin,

Hwang,

Siboni

et al. 2024

Front. Optoelectron.

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InGaN/GaN micro-light-emitting diodes (micro-LEDs) with a metal–insulator-semiconductor (MIS) structure on the sidewall are proposed to improve efficiency. In this MIS structure, a sidewall electrode is deposited on the insulating layer-coated sidewall of the device mesa between a cathode on the bottom and an anode on the top. Electroluminescence (EL) measurements of fabricated devices with a mesa diameter of 10 μm show that the application of negative biases on the sidewall electrode can increase the device external quantum efficiency (EQE). In contrast, the application of positive biases can decrease the EQE. The band structure analysis reveals that the EQE is impacted because the application of sidewall electric fields manipulates the local surface electron density along the mesa sidewall and thus controls surface Shockley–Read–Hall (SRH) recombination. Two suggested strategies, reducing insulator layer thickness and exploring alternative materials, can be implemented to further improve the EQE of MIS micro-LEDs in future fabrication. Graphical Abstract

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Section: Resultsmentioning

confidence: 99%

“…For the latter, high- κ dielectrics are preferred to reach the high electric field with a lower sidewall bias. Common materials to replace Si 3 N 4 as sidewall insulators can be Al 2 O 3 , HfO 2 and ZrO 2 [ 8 – 10 , 22 – 26 ].…”

Section: Resultsmentioning

confidence: 99%

Efficiency improvement by using metal–insulator-semiconductor structure in InGaN/GaN micro-light-emitting diodes

Yin,

Hwang,

Siboni

et al. 2024

Front. Optoelectron.

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“…It shows that the hole concentration in the mesa sidewalls region of device B is lower than that of device A, while the hole concentration in the middle mesa region of device B is higher than that of device A. 1.0×10 19 1.2×10 19 1.4×10 19 0 0.005 0.010 0.015 0.020 0 5.0x10 16 1.0x10 17 1.5x10 17 2.0x10 17 2.5x10 17 RelaƟve posiƟon (μm) It is worth noting that the secondary etched mesa for device B also contains surface defects and these are also considered in our physical model. Hence, it is necessary to extract the recombination current for devices A and B.…”

Section: Resultsmentioning

confidence: 94%

“…For that goal, our group proposed an ITO/Ta 2 O 5 /p-GaN periphery junction at the µLED mesa edge. [17] The most significant advantage of this design is that the large relative dielectric constant of 26 for the Ta 2 O 5 layer can generate energy barriers in the p-GaN layer, and this helps to confine the holes in the central region for the µLED mesa. According to the report by Kou et al, [10] the hole injection can be promoted when the surface recombination can be significantly suppressed.…”

Section: Introductionmentioning

confidence: 99%

A polarization mismatched p-GaN/p-Al_0.25Ga_0.75N/p-GaN structure to improve the hole injection for GaN based micro-LED with secondary etched mesa

Zhang¹,

Chu²,

Hang³

et al. 2023

Chinese Phys. B

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A low hole injection efficiency for InGaN/GaN micro-light-emitting diodes (μLEDs) has become one of the main bottlenecks affecting the improvement of the external quantum efficiency (EQE) and the optical power. In this work, we propose and fabricate a polarization mismatched p-GaN/p-Al0.25Ga0.75N/p-GaN structure for 445 nm GaN-based μLEDs with the size of 40 × 40 μm2, which serves as the hole injection layer. The polarization-induced electric field in the p-GaN/p-Al0.25Ga0.75N/p-GaN structure provides holes with more energy and can more facilitate the non-equilibrium holes to transport into the active region for radiative recombination. Meanwhile, a secondary etched mesa for μLEDs is also designed, which can effectively keep the holes apart from the defected region of the mesa sidewalls, and the surface nonradiative recombination can be suppressed. Therefore, the proposed μLED with the secondary etched mesa and the p-GaN/p-Al0.25Ga0.75N/p-GaN structure has the enhanced EQE and the improved optical power density when compared with the μLED without such designs.

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“…For instance, people have proposed an oxide-confined structure to reduce current diffusion to the sidewall 22 . Hang and Zhang et al employed the resistive ITO/p-GaN junction and Ta 2 O 5 high-k insulator to modulate the band structure and reduce hole concentration near damaged regions 23,24 . Kirilenko et al utilized H 2 plasma to passivate Mg acceptors of p-type layers near the sidewall and formed an insulating region to suppress carrier non-radiative recombination 25 .…”

Section: Introductionmentioning

confidence: 99%

Etching-free pixel definition in InGaN green micro-LEDs

Liu,

Lu,

Cao

et al. 2024

Light Sci Appl

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The traditional plasma etching process for defining micro-LED pixels could lead to significant sidewall damage. Defects near sidewall regions act as non-radiative recombination centers and paths for current leakage, significantly deteriorating device performance. In this study, we demonstrated a novel selective thermal oxidation (STO) method that allowed pixel definition without undergoing plasma damage and subsequent dielectric passivation. Thermal annealing in ambient air oxidized and reshaped the LED structure, such as p-layers and InGaN/GaN multiple quantum wells. Simultaneously, the pixel areas beneath the pre-deposited SiO2 layer were selectively and effectively protected. It was demonstrated that prolonged thermal annealing time enhanced the insulating properties of the oxide, significantly reducing LED leakage current. Furthermore, applying a thicker SiO2 protective layer minimized device resistance and boosted device efficiency effectively. Utilizing the STO method, InGaN green micro-LED arrays with 50-, 30-, and 10-µm pixel sizes were manufactured and characterized. The results indicated that after 4 h of air annealing and with a 3.5-μm SiO2 protective layer, the 10-µm pixel array exhibited leakage currents density 1.2 × 10−6 A/cm2 at −10 V voltage and a peak on-wafer external quantum efficiency of ~6.48%. This work suggests that the STO method could become an effective approach for future micro-LED manufacturing to mitigate adverse LED efficiency size effects due to the plasma etching and improve device efficiency. Micro-LEDs fabricated through the STO method can be applied to micro-displays, visible light communication, and optical interconnect-based memories. Almost planar pixel geometry will provide more possibilities for the monolithic integration of driving circuits with micro-LEDs. Moreover, the STO method is not limited to micro-LED fabrication and can be extended to design other III-nitride devices, such as photodetectors, laser diodes, high-electron-mobility transistors, and Schottky barrier diodes.

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A Buried HighkInsulator for Suppressing the Surface Recombination for GaN-Based Micro-Light-Emitting Diodes

Cited by 10 publications

References 22 publications

Efficiency improvement by using metal–insulator-semiconductor structure in InGaN/GaN micro-light-emitting diodes

Efficiency improvement by using metal–insulator-semiconductor structure in InGaN/GaN micro-light-emitting diodes

A polarization mismatched p-GaN/p-Al_0.25Ga_0.75N/p-GaN structure to improve the hole injection for GaN based micro-LED with secondary etched mesa

Etching-free pixel definition in InGaN green micro-LEDs

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A Buried HighkInsulator for Suppressing the Surface Recombination for GaN-Based Micro-Light-Emitting Diodes

Cited by 10 publications

References 22 publications

Efficiency improvement by using metal–insulator-semiconductor structure in InGaN/GaN micro-light-emitting diodes

Efficiency improvement by using metal–insulator-semiconductor structure in InGaN/GaN micro-light-emitting diodes

A polarization mismatched p-GaN/p-Al0.25Ga0.75N/p-GaN structure to improve the hole injection for GaN based micro-LED with secondary etched mesa

Etching-free pixel definition in InGaN green micro-LEDs

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A polarization mismatched p-GaN/p-Al_0.25Ga_0.75N/p-GaN structure to improve the hole injection for GaN based micro-LED with secondary etched mesa