Monolithically Integrated Metal/Semiconductor Tunnel Junction Nanowire Light-Emitting Diodes

We have demonstrated for the first time an <i>n</i><sup>++</sup>-GaN/Al/<i>p</i><sup>++</sup>-GaN backward diode, wherein an epitaxial Al layer serves as the tunnel junction. The resulting <i>p</i>-contact free InGaN/GaN nanowire light-emitting diodes (LEDs) exhibited a low turn-on voltage (∼2.9 V), reduced resistance, and enhanced power, compared to nanowire LEDs without the use of Al tunnel junction or with the incorporation of an <i>n</i><sup>++</sup>-GaN/<i>p</i><sup>++</sup>-GaN tunnel junction. This unique Al tunnel junction overcomes some of the critical issues related to conventional GaN-based tunnel junction designs, including stress relaxation, wide depletion region, and light absorption, and holds tremendous promise for realizing low-resistivity, high-brightness III-nitride nanowire LEDs in the visible and deep ultraviolet spectral range. Moreover, the demonstration of monolithic integration of metal and semiconductor nanowire heterojunctions provides a seamless platform for realizing a broad range of multifunctional nanoscale electronic and photonic devices.