Abstract

Different experimental and simulation techniques aiming at a better understanding of lateral mode absorption in light-emitting diodes (LEDs) are presented in this paper. A measurement of transmitted power versus propagation distance allows us to derive the absorption losses of LED layer structures at their emission wavelength. Two models for the observed intensity distribution are presented: one is based on scattering, whereas the other relies on selective absorption. Both models were applied to InGaN-on-sapphire-based LED structures. Material absorption losses of 7 cm^-1 for the scattering model and 4 cm^-1 for the absorbing-layer model were obtained. Furthermore, these values are independent of the emission wavelength of the layer structure in the 403-433-nm range. The losses are most likely caused by a thin highly absorbing layer at the interface to the substrate. In a second step, interference of the modal field profile with the absorbing layer can be used to determine its thickness (d = 75 nm) and its absorption coefficient (alpha ~ 3900 cm^-1). This method has also been tested and applied on AlGaInP-based layer structures emitting at 650 nm. In this case, the intensity decay of alpha = 30 cm-1 includes a contribution from the absorbing substrate.

© 2004 IEEE

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Other (9)

M. Rattier, H. Benisty, R. P. Stanely, J. F. Carlin, R. Houdre, U. Oesterle, C. J. M. Smith, C. Weisbuch and T. F. Krauss, "Toward ultrahigh-efficiency aluminum oxide microcavity light-emitting diodes: Guided mode extraction by photonic crystals", IEEE J. Select. Topics Quantum Electron., vol. 8, pp. 238-247, Mar.-Apr. 2002.

R. Windisch, C. Rooman, B. Dutta, A. Knoblauch, G. Borghs, G. M. Döhler and P. Heremans, "Light-extraction mechanisms in high-efficiency surface-textured light-emitting diodes", IEEE J. Select. Topics Quantum Electron., vol. 8, pp. 248-254, Mar.-Apr. 2002.

F. A. Kish, F. M. Steranka, D. C. DeFevere, D. A. Vanderwater, K. G. Park, C. P. Kuo, T. D. Osentowski, M. J. Peanasky, J. G. Yu, R. M. Fletcher, D. A. Steigerwald, M. G. Craford and V. M. Robbins, "Very high-efficiency semiconductor wafer-bonded transparent-substrate (AlxGa1-x)0.5In0.5P/GaP light-emitting diodes", Appl. Phys. Lett., vol. 64, no. 21, pp. 2839-2841, 1994.

M. O. Holcomb, M. R. Krames, G. E. Hofler, C. Carter-Coman, E. Chen, P. Grillot, K. Park, N. F. Gardner, J.-W. Huang, J. Posselt, D. Collins, S. A. Stockman, G. M. Craford, F. A. Kish, I.-H. Tan, T. S. Tan, C. P. Kocot and M. Hueschen, "High power truncated-inverted pyramid (AlxGa1-x)0.5In0.5P light-emitting diodes", in Proc. SPIE, vol. 3938, 2000, pp. 77-81.

S. S. Schad, B. Neubert, M. Seyboth, F. Habel, C. Eichler, M. Scherer, P. Unger, W. Schmid, C. Karnutsch and K. P. Streubel, "Absorption of guided modes in light emitting diodes", in Proc. SPIE, vol. 4996, 2003, pp. 10-17.

M. Mannoh, J. Hoshina, S. Kamiyama, H. Ohta, Y. Ban and K. Ohnaka, "High power and high-temperature operation of GaInp/AlGaInp strained multiple quantum well lasers", Appl. Phys. Lett. , pp. 1173-1175, 1993.

H. D. Summers and P. Rees, "Experimental investigation of the differential gain in semiconductor lasers and its influence on Q-switching performance", Appl. Phys. Lett., pp. 2009-2011, 1996.

G. M. Laws, E. C. Larkins, I. Harrison, C. Molloy and D. Somerford, "Improved refractive index formulas for the AlGaN and InGaN alloys", J. Appl. Phys., vol. 89, no. 2, pp. 1108-1115, 2001.

S. S. Schad, B. Neubert, J. Brüning, C. Eichler, F. Habel, F. Scholz, P. Unger and D. Hofstetter, "Absorption in InGaN-on-sapphire LED-structures: Comparison between the photocurrent measurement method (PMM) and the photothermal deflection spectroscopy", in Proc. SPIE, Light-Emitting Diodes: Research, Manufacturing, Applications , vol. 5336, 2004, to be published.

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