53.1: <i>Invited Paper:</i> Process optimization of passive matrix GaN Micro‐LED displays

Zhang, Zhi; Nie, Junyang; Chen, Kongjie; Jiang, Bingxin; He, Shuang; Yang, Tianxi; Sun, Jie; Su, Anjun; Chen, Nianrui; Zhou, Jun; Guo, Tailiang; Yan, Qun

doi:10.1002/sdtp.16008

Cited by 3 publications

(4 citation statements)

References 17 publications

(13 reference statements)

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“…Completed devices were first tested to characterize leakage current as low leakage is essential for realizing functional passive matrix displays [15][16][17][18] . This test was carried out by applying a 0-30 V sweep across the ncontacts of adjacent test devices separated by trenches varying from 30 µm to 100 µm in width.…”

Section: Resultsmentioning

confidence: 99%

“…The second approach allows for the theoretical use of a monolithic blue emitting GaN display, with some pixels converted to green and red emission by application of phosphors. In a monolithic GaN display, current leakage between pixels is an issue due to challenges in growing truly intrinsic, insulating u-GaN [13][14][15][16][17][18][19][20] . In a basic m x n passive matrix array which has m rows and n columns, m + n control signals are used to address the elements of the display.…”

Section: Introductionmentioning

confidence: 99%

“…Mg activation becomes less effective as device dimensions increase, due to increased out-diffusion path lengths of hydrogen. The second approach is to simply etch completely through the GaN LED epi all the way to the substrate [17][18][19][20] . Most GaN is grown on sapphire, an excellent insulator, so a through-epi etch fully eliminates leakage between pixel columns.…”

Section: Introductionmentioning

confidence: 99%

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Photoresist planarized trench isolation for monolithic GaN µLED displays

Melanson

Seitz

Zhang

2023

Gallium Nitride Materials and Devices XVIII

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Micro-Light-Emitting Diode (µLED) displays have seen increasing interest over the past decade due to their promising advantages over other display technologies, especially in applications requiring extremely high resolutions such as virtual and alternate reality headsets. Most modern full-color µLED displays rely on red, green, and blue (RGB) pixels based on different material systems combined together on a thin-film transistor back panel, which is often costly and has poor yield. An alternative approach is to create a monolithic display in the GaN/InGaN material system, capable of covering the entire visible spectrum through tuning of quantum well (QW) Indium content or phosphor down conversion. However, monolithic GaN displays present the issue of pixel isolation, as the lack of truly insulating undoped GaN (u-GaN) makes it difficult to electrically isolate rows or columns of µLEDs from one another.In this work, we demonstrate a novel solution to this issue which utilizes photoresist to fill deep trench isolation features, enabling interconnection of µLED p-contacts in a single-color passive matrix display. A photoresist layer is used to fill deep trenches isolating columns of µLEDs from one another. This photoresist layer is patterned and baked at 250 °C for 30 minutes, crosslinking it and making it extremely durable. This process allows for formation of p-interconnects using liftoff, and avoids the issues involved in bridging high aspect ratio trenches. This photoresist planarized trench isolation process could contribute to creation of improved monolithic full color µLED displays which require multiple deep isolation features to be bridged by conductive interconnects.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photoresist planarized trench isolation for monolithic GaN µLED displays

Melanson

Seitz

Zhang

2023

Gallium Nitride Materials and Devices XVIII

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“…Compared with FPGA, it is more convenient to verify the quality of the PM device. Second, the PM device process technology has also been optimized by adding the GaN as the substrate to avoid the bulging of the p-lines, resulting in the successful preparation of the PM device with excellent performance [14]. Section 3 adopts the row-column integration and two-wire serial transmission, which avoids high contrast and cross-version coupling.…”

Section: Introductionmentioning

confidence: 99%

Passive matrix Micro-LED display driven by STM32 microcontroller using a two-wire serial transmission method

Chen

et al. 2023

J. Phys.: Conf. Ser.

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In this study, the STM32 microcontroller is used to drive a passive matrix (PM) Micro-LED through two-wire serial transmission and row-column integration. STM32 exhibits superior properties, including simple-to-operate, cost-friendly, and flexible programming. Moreover, it has a lower cost and more straightforward implementation for testing the quality of the device and realizing the graphics. In this design, the connection between the STM32 and the PM array is realized by an LED driver board and flexible printed circuit (FPC) structure. The two-wire serial protocol and row-column integration are adopted, which not only optimizes the circuit structure but also avoids coupling problems. Compared to the existing structures, it is more concise that only four connecting wires are required to transmit data in display devices of any resolution. Besides, the problem of graphics distortion is solved through two buffers to form a data handshake. Using this method, the blue PM array, which has a resolution of 48 × 48, a refresh rate of 60 Hz, a pixel size of 300 μm, and a luminous area of 50 μm, is successfully realized. In addition, p-metal fractures caused by the bulge in the p-lines are also resolved by adding the GaN as a raised substrate.

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