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

Correspondence to: P. Waltereit Correspondence and requests for materials should be addressed to P.W. (e-mail: Email: walter@pdi-berlin.de).

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 generation^{4, 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.