Beam-shaping properties of InGaN thin-film micro-cavity light-emitting diodes with photonic crystals

Bergenek, K.; Wiesmann, Christopher; Zull, H.; Rumbolz, C.; Wirth, R.; Linder, N.; Streubel, K.; Krauss, Thomas F.

doi:10.1117/12.807617

Cited by 10 publications

(13 citation statements)

References 23 publications

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“…Here the gain is less than unity due to the contribution of sidewall emission at large angles and the detuned half-cavity 7 formed by the mirror and first quantum well. We note the excellent agreement between our results and those of Bergenek et al, 4 who observed similar directionality gain for 850-nm-thick PhC LEDs with an a / ratio close to ours. It is also worth noting that the directionality gain will of course depend on what fraction of the total emission is due to PhC extraction.…”

supporting

confidence: 81%

“…The directionality gain is then defined as the power emitted into a given acceptance angle by the PhC LED, divided by the power emitted into the same aperture by the Lambertian emitter. 4 As shown in Fig. 2͑b͒, both the thin and thick PhC LEDs yielded a substantial directionality gain for small acceptance angles.…”

mentioning

confidence: 89%

“…In addition, it has been suggested that thinner PhC LEDs may afford more directional far-field patterns, since their emission is concentrated into a smaller number of guided modes. 3,4 While the epitaxial thickness of conventional InGaN LEDs on sapphire is generally fixed by growth constraints to several microns or more, thin-film LEDs offer greater flexibility since the n-GaN can be thinned down after removal of the sapphire substrate. Several thin-film InGaN PhC LEDs with submicron thickness have now been reported, [3][4][5][6] including a 700-nm-thick device with an unencapsulated extraction efficiency of 73%.…”

mentioning

confidence: 99%

“…3,4 While the epitaxial thickness of conventional InGaN LEDs on sapphire is generally fixed by growth constraints to several microns or more, thin-film LEDs offer greater flexibility since the n-GaN can be thinned down after removal of the sapphire substrate. Several thin-film InGaN PhC LEDs with submicron thickness have now been reported, [3][4][5][6] including a 700-nm-thick device with an unencapsulated extraction efficiency of 73%. 5 However, the impact of thickness on the directionality and extraction efficiency has not been studied in detail.…”

mentioning

confidence: 99%

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Interplay of cavity thickness and metal absorption in thin-film InGaN photonic crystal light-emitting diodes

Rangel

Matioli

Chen

et al. 2010

Applied Physics Letters

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Thin-film InGaN photonic crystal (PhC) light-emitting diodes (LEDs) with a total semiconductor thickness of either 800 nm or 3.45 μm were fabricated and characterized. Increased directional radiance relative to Lambertian emission was observed for both cases. The 800-nm-thick PhC LEDs yielded only a slight improvement in total light output over the 3.45-μm-thick PhC LEDs. Simulations indicate that, except for ultrathin devices well below 800 nm, the balance between PhC extraction and metal absorption at the backside mirror results in modal extraction efficiencies that are almost independent of device thickness, but highly dependent on mirror reflectivity.

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confidence: 81%

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confidence: 89%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Interplay of cavity thickness and metal absorption in thin-film InGaN photonic crystal light-emitting diodes

Rangel

Matioli

Chen

et al. 2010

Applied Physics Letters

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“…Various approaches have been adopted to extract the light trapped in LEDs. A great number of efforts have been made to use photonic crystals to improve the light extraction or control the radiation pattern of various types of GaN-based LEDs, such as commercial LEDs with GaN on sapphire substrate [1][2][3][4][5][6][7][8][9][10][11][12], thin-film LEDs [4,[13][14][15], flip-chip LEDs [16] and micro-cavity LEDs [17]. Though the coupling between the photonic crystal and guided modes is different due to the different types of LEDs, the strategy of using a PhC grating in most publications mainly relies on Bragg diffraction of the trapped guided modes from the LEDs.…”

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confidence: 99%

Lattice-parameter effects on diffracted transmission of GaN two-dimensional square-lattice photonic crystals

Xiong

Zhang

Kang

et al. 2010

Sci. China Technol. Sci.

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The lattice-parameter effects on the diffracted transmission of GaN square-lattice photonic crystals (2PhC) at the wavelength of 460 nm were studied by using a rigorous coupled wave analysis (RCWA). The impacts of lattice parameters on the diffracted transmission are calculated in the ranges for lattice pitch from 100 nm to 2000 nm, fill factor from 0.1 to 0.9 and grating height from 100 nm to 1000 nm, respectively. Our simulation results confirm that the lattice pitch is the dominant factor of the diffraction. It determines how many orders of diffraction occur by the 2PhCs. The larger the lattice pitch, the higher the diffraction orders come into play. Moreover, besides the first-order Bragg diffraction, higher diffraction orders from large pitches of PhCs are also beneficial to the light extraction improvement. The higher enhancement factors of the integrated transmission were obtained from a wide range of pitches with micro-scale GaN 2PhCs. Three different diffraction mechanisms through wave vector analysis were used to discuss the simulation results. GaN, photonic crystal, diffractionCitation:Xiong C, Zhang B, Kang X N, et al. Lattice-parameter effects on diffracted transmission of GaN two-dimensional square-lattice photonic crystals.

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Directionality control through selective excitation of low-order guided modes in thin-film InGaN photonic crystal light-emitting diodes

Rangel¹,

Matioli²,

Choi³

et al. 2011

Applied Physics Letters

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This letter explores the impact of quantum well placement and photonic crystal (PhC) etch depth on the emission directionality of thin-film InGaN PhC light-emitting diodes (LEDs). The far-field pattern of 800-nm-thick PhC LEDs is tuned by varying only the etch depth of a surface-patterned hexagonal PhC from 90 to 440 nm. This dependence on etch depth is shown to arise from the preferential excitation of a subset of the allowed guided modes. Selective excitation of the TE0 and TE1 modes is utilized to achieve a vertically directional emission pattern comprised of only these two modes.

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Beam-shaping properties of InGaN thin-film micro-cavity light-emitting diodes with photonic crystals

Cited by 10 publications

References 23 publications

Interplay of cavity thickness and metal absorption in thin-film InGaN photonic crystal light-emitting diodes

Interplay of cavity thickness and metal absorption in thin-film InGaN photonic crystal light-emitting diodes

Lattice-parameter effects on diffracted transmission of GaN two-dimensional square-lattice photonic crystals

Directionality control through selective excitation of low-order guided modes in thin-film InGaN photonic crystal light-emitting diodes

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