Research ArticleAPPLIED SCIENCES AND ENGINEERING

Remote heteroepitaxy of GaN microrod heterostructures for deformable light-emitting diodes and wafer recycle

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Science Advances  03 Jun 2020:
Vol. 6, no. 23, eaaz5180
DOI: 10.1126/sciadv.aaz5180
  • Fig. 1 Remote heteroepitaxy of GaN MR heterostructures on c-Al2O3 across graphene.

    (A) Photograph of EL light emission from MR LED in a bent form. (B) Cross-sectional schematic of MR heterostructures grown on graphene-coated c-Al2O3 wafer. (C) Annular bright-field (ABF) STEM image of remote epitaxial heterointerface of GaN/graphene/c-Al2O3 focused on graphene. The location of the doubly stacked SLG is marked with red wedges. Atomic-resolution filtered ABF STEM images of (D) GaN MR and (E) c-Al2O3 taken around the heterointerface area. (F) Tilt-view FE-SEM image of as-grown MR LED arrays of radial p-n junction heterostructures. (G) Photograph of EL light emission from 5 mm by 5 mm area MR LED in a flat form at 100 mA. Photomicrographs of MR LED (H) without and (I) with current injection of 100 mA, taken from the boxed area in (G). The off-state photomicrograph of (H) was taken under normal lamp illumination conditions.

  • Fig. 2 Diversely deformable MR LED.

    (A) Schematics illustrating key procedures for fabricating the deformable LED, including remote heteroepitaxy of MR LED arrays and transfer onto conducting metal plate. (B) A series of photographs of cyan MR LED (λ = 500 nm) deformed in various shapes, such as twisted, 90°-folded crumpled, and 180°-folded forms, operated at 100 mA. The inset in the rightmost image of (B) is a schematic illustrating the geometry of MR arrays in the folded form. (C) Photographs of blue MR LED (λ = 450 nm) mounted on various surfaces, including a pen and thin wall edge of plastic box, operated at 100 mA. It is noted that the blue MR LED shown in (C) is produced from a recycled wafer. (D) Photographs of 10 mm by 10 mm MR LED (λ = 450 nm) tailored to be fitted to two back legs of a minifigure (left two panels); photographs of LED-adhered LEGO minifigure with different leg postures (right three panels). The LED was operated at 100 mA. Scale bars (D), 10 mm. Photo credit: Junseok Jeong, Sejong University.

  • Fig. 3 Electrical and electroluminescent properties and repetitive bending cycle test.

    (A) I-V characteristic curves and (B) EL spectra of the MR LED bent at radii of curvatures of ∞ (blue lines) and 10 mm (red lines). For the EL measurement of (B), the LED was operated at the same current of 100 mA. (C) I-V characteristic curves measured after repeating the bending cycles from 1 to 1000 times between radius curvatures ∞ and 10 mm. (D) EL peak position (red empty squares) and EL intensity (blue solid circles) measured as a function of bending cycle up to 1000 times. For the measurements, the MR LED was flattened and operated at 100 mA after the bending cycles. Insets are photographs of EL emission after bending cycles of 0, 500, and 1000 times. A.U., arbitrary units.

  • Fig. 4 DFT calculation.

    (A) Atomic configuration of BLG/c-Al2O3 substrate with in-plane alignment of [1¯21¯0]BLG║[11¯00]sapphire. Plan-view charge density (ρ) contour maps of BLG/c-Al2O3, tomographically sectioned at the heights of (B) 4.4 Å and (C) 7.3 Å apart from the topmost surface of Al2O3, as marked with blue lines in (A). (D) Cross-sectional ρ distribution contour map sectioned across the three Al atoms, as marked with a red line in (B) and (C). The maps were simulated by calculating ρBLG/sapphire − ρBLG to eliminate the background charge density coming from graphene layers. The ρ simulation was performed in the range between −8 × 10−5 e Å−3 and 8 × 10−5 e Å−3. The locations of Al and O atoms in the plan-view contour maps are denoted as large and small dot-line circles, respectively, as marked in the inset box.

  • Fig. 5 Wafer recycle.

    (A) Plan-view FE-SEM images of remote heteroepitaxial MR LED arrays grown on graphene-coated virgin (left) and recycled (right) wafers. The yellow arrows indicate that the MRs on both the virgin and recycled wafers have homogeneous in-plane alignment of hexagonal symmetry of MR sidewalls. (B) I-V characteristic curves and (C) EL spectra of MR LEDs fabricated by using virgin (blue line) and recycled (red line) wafers. The insets in (C) are photographs of EL light emission from the MR LEDs fabricated with virgin and recycled wafers in a dark room. (D) Photographs of blue EL emission of the LEDs attached on the surface of finger-sized bottle in the bent form at an Rb of 10 mm. The EL spectra and photographs were obtained at the same applied current of 100 mA and the EL measurement conditions. Photo credit: Junseok Jeong, Sejong University.

Supplementary Materials

  • Supplementary Materials

    Remote heteroepitaxy of GaN microrod heterostructures for deformable lightemitting diodes and wafer recycle

    Junseok Jeong, Qingxiao Wang, Janghwan Cha, Dae Kwon Jin, Dong Hoon Shin, Sunah Kwon, Bong Kyun Kang, Jun Hyuk Jang, Woo Seok Yang, Yong Seok Choi, Jinkyoung Yoo, Jong Kyu Kim, Chul-Ho Lee, Sang Wook Lee, Anvar Zakhidov, Suklyun Hong, Moon J. Kim, Young Joon Hong

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