Excitonic emission dynamics at cryogenic- and above room temperature in high brightness sub-micron fin LED and Lasers

A n-ZnO fin - p-GaN UV light-emitting diode (LED) with sub-μm m2 lateral size is presented that exceeds the output power of previous nanoscale light sources by a factor of 1000, generating 1 $\mu m$ Watt to 20 $\mu m$ Watt power. To better understand the origin of the improved efficiency in these nanostructures relative to other nanostructures, we will investigate the collection of electrons and holes by fins at cryogenic- and room temperatures. At low temperatures of about 6 K, electron-hole recombination dominantly occurs in the GaN side. As the temperature increases to RT, the fin LED radiative recombination migrates to the ZnO fin and becomes dominantly excitonic. At higher temperatures, results show ZnO performs better than GaN as the oscillator strength of the excitonic emission in ZnO stays independent of the heterojunction temperature. We will also discuss the structural advantage of fins in heat dissipation and their droop-free behavior at high temperatures indicating their importance in realization of high temperature UV LEDs and lasers.