Tunable nanostructured distributed Bragg reflectors for III-nitride optoelectronic applications.

Highly reflective and conductive distributed Bragg reflectors (DBRs) are the key for high-performance III-nitride optoelectronic devices, such as vertical cavity surface emitting lasers (VCSELs), but they still suffer from lack of lattice-matched conductive DBR and uncontrollable processes. In this work, nanostructured GaN-based DBRs were fabricated and optimized both experimentally and simulatively using electrochemical etching (EC) in different electrolytes using the transfer-matrix method (TMM) to obtain uniform wafer scale, highly reflective and conductive reflectors for the application of GaN-based optoelectronics. The results revealed that a nanostructured GaN-based DBR with high reflectivity (>93%) and broad stopband (∼80 nm) could be achieved in neutral sodium nitrate by EC, and the nanostructured GaN DBR with a full visible spectrum range could be designed by tuning the thickness of the nanostructured GaN DBR layers. The photoluminescence (PL) and light-out power enhancements of the GaN-based micro-LED by incorporating the fabricated nanostructured GaN-based DBR were 6 times and 150% without the degradation of electrical performance, respectively, which contributed to strong light scattering from the DBR layers. We believe that this work will pave a way to obtain high-performance GaN-based optoelectronic devices and guide the applications in the field of flexible devices and biomedical sensors.