Reobservation of GaN Nanostructures for Random Laser

Abstract

Unlikely a conventional laser, random laser has the scattering medium in which itself serves as virtual cavity and emits the light in different directions. Recently, scattering medium of random laser has been designed such as photonic crystals, quantum dots, and semiconductor.[1] Randomly distributed nanostructures have the potential to be used as scattering medium of random laser. As mechanism of light localization for random laser is scattering in gain medium, one of the main factors of random lasing is density of nanostructures.[2] Here, we fabricate GaN nanostructures, as shown in Figure 1, via tunable density of disordered SiO2 mask. First, we grow SiO2 on GaN on sapphire substrate via plasma enhanced chemical vapor deposition and Ag using electron beam evaporator. After that, we process thermal dewetting of Ag for etching mask, and dry etching of SiO2 by reactive ion etching, and Ag removal via HNO3 solution. Finally, we implement GaN nanostructures by inductively coupled plasma reactive ion etching with SiO2 mask and buffered oxide etchant for SiO2 removal. We show various density of GaN nanostructures which exhibit the different number of lasing mode. Further, we inspect the tendency of random laser phenomenon by line scanning. With this spatial scanning, we can exhibit spatial characteristic of random lasing, which show the probability of random lasing intensity above the threshold is governed by Poisson distribution.