Formation of β-Be₃N₂ nanocrystallites in Be-implanted GaN

Abstract A small Be ion dose of 5 × 10¹⁴ cm⁻² was implanted in a 2 μm thick GaN epilayer at an energy of 50 keV. The sample was characterized by high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy techniques after a post-implantation rapid thermal annealing (RTA) treatment. The HRTEM images show the crystallographic (1 1 0) and (0 0 2) planes of β-Be₃N₂. Two characteristic parallelograms drawn in Fast Fourier transform (FFT) image support the formation of β-Be₃N₂ nanocrystallites in RTA treated sample. Two Raman peaks at 168 and 199 cm⁻¹ are observed in the Raman spectrum of the sample that are assigned to β-Be₃N₂ on the basis of group theory and HRTEM data. The Raman peak at 168 cm⁻¹ is found close to the K point in the first Brillouin zone of β-Be₃N₂ while the peak at 199 cm⁻¹ is assigned as a combination mode of the fundamental Raman modes of β-Be₃N₂.