Temperature-dependent photoluminescence in Ge: Experiment and theory

José Menéndez, Christian D. Poweleit, Sean E. Tilton

Research output: Contribution to journalArticle

Abstract

We report a photoluminescence study of high-quality Ge samples at temperatures 12K≤T≤295K, over a spectral range that covers phonon-assisted emission from the indirect gap (between the lowest conduction band at the L point of the Brillouin zone and the top of the valence band at the Γ point), as well as direct gap emission (from the local minimum of the conduction band at the Γ point). The spectra display a rich structure with a rapidly changing line shape as a function of T. A theory is developed to account for the experimental results using analytical expressions for the contributions from LA, TO, LO, and TA phonons. Coupling of states exactly at the Γ and L points is forbidden by symmetry for the latter two phonon modes, but becomes allowed for nearby states and can be accounted for using wave-vector dependent deformation potentials. Excellent agreement is obtained between predicted and observed photoluminescence line shapes. A decomposition of the predicted signal in terms of the different phonon contributions implies that near-room temperature indirect optical absorption and emission are dominated by "forbidden" processes, and the deformation potentials for allowed processes are smaller than previously assumed.

Original languageEnglish (US)
Article number195204
JournalPhysical Review B
Volume101
Issue number19
DOIs
StatePublished - May 15 2020

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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