Structural, optical and electronic properties of a Mg incorporated GaN nanowall network

Abstract

We report the growth of a Mg incorporated GaN nanowall network (NwN) by using a plasma assisted molecular beam epitaxy (PA-MBE) system that was 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 PL enhancement (≈3.2 times) in nominally and moderately Mg incorporated GaN compared to that of an undoped NwN. Two distinct (and broad) blue luminescence peaks appear at 2.95 and 2.70 eV for the heavily Mg incorporated (10²⁰ atoms per cm³) GaN, of which the 2.95 eV peak is sensitive to annealing. The incorporated Mg concentration is estimated to be 10²⁰ atoms per cm³ while retaining its band edge emission at ≈3.4 eV. XPS valence band spectra shows a shift in the Fermi level towards Valence Band Maximum (VBM) and the increase in Mg flux confirms the formation of p-type GaN. Mg accumulation at the nanowall surface and the GaN/Al₂O₃ interface was observed from SIMS measurements.