GaN Nanowall Network: A new possible route to obtain efficient p-GaN and   enhanced light extraction
  We demonstrate that GaN formed in a Nanowall Network (NwN) morphology can overcome fundamental limitations in optoelectronic devices, and enable high light extraction and effective Mg incorporation for efficient p-GaN. We report the growth of Mg doped GaN Nanowall network (NwN) by plasma assisted molecular beam epitaxy (PA-MBE) that is characterized by Photoluminescence (PL) spectroscopy, Raman spectroscopy, high-resolution X-ray diffraction (HR-XRD), X-ray photoelectron spectroscopy (XPS) and Secondary ion mass spectroscopy (SIMS). We record a photo-luminescence enhancement ($ \approx $3.2 times) in lightly doped GaN as compared to that of undoped NwN. Two distinct (and broad) blue luminescence peaks appears at 2.95 and 2.7 eV for the heavily doped GaN (Mg $>10^{20}$ atoms $cm^{-3}$), of which the 2.95 eV peak is sensitive to annealing is observed. XPS and SIMS measurements estimate the incorporated Mg concentration to be $10^{20}$ atoms $cm^{-3}$ in GaN NwN morphology, while retaining its band edge emission at $\approx$ 3.4 eV. A higher Mg accumulation towards the GaN/Al$_2$O$_3$ interface as compared to the surface was observed from SIMS measurements. 
Sanjay Kumar Nayak, Mukul Gupta, S.M. Shivaprasad
cond-mat.mtrl-sci