Microtube Light-Emitting Diode Arrays with Metal Cores

We report the fabrication and characteristics of vertical microtube light-emitting diode (LED) arrays with a metal core inside the devices. To make the LEDs, gallium nitride (GaN)/indium gallium nitride (In_xGa_1-xN)/zinc oxide (ZnO) coaxial microtube LED arrays were grown on an n-GaN/c-aluminum oxide (Al₂O₃) substrate. The microtube LED arrays were then lifted-off the substrate by wet chemical etching of the sacrificial ZnO microtubes and the silicon dioxide (SiO₂) layer. The chemically lifted-off LED layer was then transferred upside-down on other supporting substrates. To create the metal cores, titanium/gold and indium tin oxide were deposited on the inner shells of the microtubes, forming n-type electrodes inside the metal-cored LEDs. The characteristics of the resulting devices were determined by measuring electroluminescence and current-voltage characteristic curves. To gain insights into the current-spreading characteristics of the devices and understand how to make them more efficient, we modeled them computationally.