Improved crystalline quality of Al-rich n-AlGaN by regrowth on nanoporous template fabricated by electrochemical etching

We report the regrown Al-rich of n-AlGaN material with improved crystalline quality and reduced stress on nanoporous AlGaN template, which was prepared by the electrochemical etching (EC). First, the EC of Al-rich AlxGa1-xN (x > 50 % ) material was investigated to get suitable nanoporous template. Various anodizing voltage and anodizing time were applied to fabricate the nanoporous AlGaN template. The nanopore size and density were found to increase as the anodizing voltage and the anodizing time increase. Moreover, branching pores and vertical pores were apt to be formed at low and high voltages, respectively. Photoluminescence (PL) measurement and Raman spectra indicate that the nanoporous AlGaN materials exhibit higher PL intensity and dramatical release of stress compared to the as-grown AlGaN films due to the presence of nanopores. Furthermore, the nearly stress-free regrown n-AlGaN with high quality using optimized nanoporous AlGaN material as the template was also obtained, which demonstrates that the nanoporous AlGaN template could potentially be applied to heteroepitaxy of efficient AlGaN-based ultraviolet optoelectronic.