Using Raman Spectroscopy to Understand Phonon Modes of Semicondcting Ternary Nitrides

Heterovalent ternary nitride crystals have significant promise in their potential applications due to their unique band-structure engineering capabilities. These crystals are integrable with binary nitrides, which revolutionized the solid state lighting industry and, recently, have been shown to be efficient silicon replacements within power electronics. The cation sublattice ordering and the structural periodicity of ternary nitrides greatly impacts their band gaps and lattice constants. Raman microscopic spectral analysis of crystal lattices detects phonon modes to give insight into the cation ordering. A Raman microscope is being constructed with an integrated fiber optic system between a BX60 Olympus confocal microscope, a laser, and a HoloSpec spectrometer; the inelastically scattered photons will be collected via an iDus 420 series CCD. The purpose of the microscope is to gain not only a spatial understanding of the samples by exploring the homogeneity of single crystal films on the micron scale, but also to image crystallites precipitated from and embedded within a solute metal alloy. Multiple crystals will be analyzed including synthesized MgSnN2 and materials structurally related to LiGaO2; various crystal recipes will be compared to explore the results of different growth procedures. These results may improve designs of future crystal growth methods to characterize and control the cation ordering within these materials.