Electrically pumped ultraviolet lasing in polygonal hollow microresonators: investigation on optical cavity effect.

Electrically driven ultraviolet lasing was realized in two-dimensional ZnO nanowall networks from Au/MgO/n-ZnO/n-GaN/In structure, and whispering gallery type resonant modes are responsible for the lasing action. We present a comparative study on lasing action based on nanowall networks with different micro-hole sizes. The representative diode (Device II) with a moderate micro-hole size exhibits an ultralow threshold current density of 1.01  A/cm, and the lasing action can be sustained at a temperature up to ∼413  K, showing a good temperature tolerance. Moreover, the corresponding characteristic temperature for Device II was derived as ∼91.4  K. It can be qualitatively anticipated that this work will provide instructive guidelines for fabrication and development of high-performance ultraviolet laser diodes by using two-dimensional ZnO nanowall networks as the lasing gain media.