Temperature-dependent photoluminescence in Ge: Experiment and theory

Article

关键词: INTERVALLEY DEFORMATION POTENTIALS;    RADIATIVE RECOMBINATION;    OPTICAL-ABSORPTION;    RAMAN-SCATTERING;    FREE-EXCITON;    ENERGY-GAP;    LINE-SHAPE;    SI;    PHONON;    LUMINESCENCE;   

DOI  :  10.1103/PhysRevB.101.195204

来源: SCIE

【 摘 要 】

We report a photoluminescence study of high-quality Ge samples at temperatures 12 K <= T <= 295 K, 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 Gamma point), as well as direct gap emission (from the local minimum of the conduction band at the Gamma 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 Gamma 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.

【 授权许可】

Free