We have demonstrated hole injection through a tunnel junction embedded in the GaN-based light emitting diode structure. The tunnel junction consists of 30 nm GaN:Si<SUP>++</SUP> and 15 nm InGaN:Mg<SUP>++</SUP> grown on a GaN-InGaN quantum well heterostructure. The forward voltage of the light emitting diode, included the voltage drop across the reverse-biased tunnel junction, is 4.1 V at 50 Z/cm$_2), while that of a standard light emitting diode with a conventional contact structure is 3.5 V. The light output of the diode with the tunnel junction is comparable to that of the standard device. We then employed the tunnel junction in vertical cavity surface emitting laser structures and dual-wavelength light emitters. In the vertical cavity structure, a good lateral current spreading was accomplished, resulting in uniform emission pattern. The dual-wavelength light emitter has been operated as a three- terminal device with independent electrical control of each LEDs to a nsec time scale.
Currently, commercial LEDs based on AlGaInN emit light efficiently from the ultraviolet-blue to the green portion of the visible wavelength spectrum. Data are presented on AlGaInN LEDs grown by organometallic vapor phase epitaxy (OMVPE). Designs for high-power AlGaInN LEDs are presented along with their performance in terms of output power and efficiency. Finally, present and potential applications for high-power AlGaInN LEDs, including traffic signals and contour lighting, are discussed.