High-quality cubic and hexagonal InN crystals studied by micro-Raman scattering and electron backscatter diffraction

Abstract

Large InN microcrystals grown by molecular beam epitaxy are investigated by micro-Raman spectroscopy and electron backscatter diffraction (EBSD). High-quality (phonon linewidths between 1.5 and 2 cm−1) cubic and hexagonal crystals are identified with Raman mapping by the observation of the respective characteristic phonon modes. The unexpected occurrence of metastable cubic InN crystals is confirmed by EBSD measurements. The cubic microcrystals are revealed by EBSD to be single-crystalline and to exhibit <1 1 1> orientation. The transverse (TO) and longitudinal-optical (LO) zone-center phonon frequencies of cubic InN are found to be 463 and 584 cm−1, respectively. The bulk carrier density in the microcrystals lies in the range of 2–3 × 1017 cm−3 as determined by the analysis of LO phonon-plasmon-coupled modes in the Raman spectra.