Phonon and Raman Spectra of LiGa₅O₈

LiGa₅O₈ is a spinel type cubic structure, was recently grown in thin film form and remarkably found to be p-type [1]. This is important for ultrawide band gap semiconductors because p-type doping is rare in such materials. LiGa₅O₈ has an optical gap of about 5.5 eV.[2] While the origin of p-type doping is not yet clear in spite of theoretical exploration of various candidate acceptors via density functional calculations, [2] it has increased the interest in this system via various characterization methods. Here we use density functional perturbation theory (DFPT) calculations using the Abinit code with the projector augmented-wave technique to study the Phonon, Infrared Absorption, and Raman Spectra in LiGa₅O₈. A symmetry analysis of the phonons is presented and used to label the phonon modes, and the oscillator strengths and Raman intensities are evaluated. There are 21 infrared active T1 modes, 6 A1, 14 E, and 20 T2 Raman active modes at the Brillouin zone center. The density of phonon states will also be presented.

[1] K. Zhang et al. Adv. Electron. Mater. 2300550 (2023)

[2] W.R.L. Lambrecht, J. Vac. Sci. Technol. A42, 022705 (2024)

[3] K. Dabsamut et al. J. Appl. Phys. 135, 235707 (2024)