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Nitride semiconductors free of electrostatic fields for efficient white light-emitting diodes

Nature volume 406, pages 865–868 (2000)Cite this article

Abstract

Compact solid-state lamps based on light-emitting diodes (LEDs)1,2 are of current technological interest as an alternative to conventional light bulbs. The brightest LEDs available so far emit red light and exhibit higher luminous efficiency than fluorescent lamps. If this luminous efficiency could be transferred to white LEDs, power consumption would be dramatically reduced, with great economic and ecological consequences. But the luminous efficiency of existing white LEDs is still very low, owing to the presence of electrostatic fields within the active layers3. These fields are generated by the spontaneous and piezoelectric polarization along the [0001] axis of hexagonal group-III nitrides—the commonly used materials for light generation4,5,6. Unfortunately, as this crystallographic orientation corresponds to the natural growth direction of these materials deposited on currently available substrates7. Here we demonstrate that the epitaxial growth of GaN/(Al,Ga)N on tetragonal LiAlO2 in a non-polar direction allows the fabrication of structures free of electrostatic fields, resulting in an improved quantum efficiency. We expect that this approach will pave the way towards highly efficient white LEDs.

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Figure 1: Calculated band profiles in (5 nm GaN)/(10 nm Al 0.1Ga0.9N) quantum wells.
Figure 2: Structural characterization of hexagonal GaN.
Figure 3: Symmetric triple-crystal ω–2θ X-ray diffraction scans of a GaN(1&1macr;00) film grown on γ-LiAlO2(100) and a GaN(0001) film grown on 6H-SiC(0001).
Figure 4: The effect of electric polarization on the emission characteristics of GaN/(Al,Ga)N multiple quantum wells (MQWs).

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Acknowledgements

We thank O. Mayrock and H.-J. Wünsche for help in the calculation of single-particle wavefunctions and exciton binding energies. This work was supported in part by the Volkswagen-Stiftung.

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  1. Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, Berlin, D-10117, Germany

    P. Waltereit, O. Brandt, A. Trampert, H. T. Grahn, J. Menniger, M. Ramsteiner, M. Reiche & K. H. Ploog

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Waltereit, P., Brandt, O., Trampert, A. et al. Nitride semiconductors free of electrostatic fields for efficient white light-emitting diodes. Nature 406, 865–868 (2000). https://doi.org/10.1038/35022529

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