title: Optical properties of coupled three-dimensional Ge quantum dot crystals.
abstract: We report on optical properties of coupled three-dimensional (3D) Ge quantum dot crystals (QDCs). With increasing the vertical periodic number of the QDCs, the photoluminescence (PL) spectral linewidth decreased exponentially, and so did the peak energy blueshift caused by increasing excitation power, which are attributed to the electronic coupling and thus the formation of miniband. In the PL spectra, the relative intensity of the transverse-optical (TO) phonon replica also decreases with increasing the vertical periodic number, which is attributed to the increased Brillouin-zone folding effect in vertical direction and therewith the relaxation of indirect transition nature of exciton recombination. Besides, the optical reflectivity at the interband transition energy was much more reduced for the QDCs than for the in-plane disordered QDs grown with the same parameters, indicating a higher interband absorption of the QDCs due to the miniband formation.
authors.affiliation: State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures Ministry of Education and Department of Physics, Fudan University, Shanghai 200433, China.
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Ma
authors.forename: Zhenyang
authors.initials: Z
authors.lastname: Zhong
authors.forename: Quan
authors.initials: Q
authors.lastname: Lv
authors.forename: Weiyang
authors.initials: W
authors.lastname: Qiu
authors.forename: Xinjun
authors.initials: X
authors.lastname: Wang
authors.forename: Tong
authors.initials: T
authors.lastname: Zhou
authors.forename: Yongliang
authors.initials: Y
authors.lastname: Fan
authors.forename: Zuimin
authors.initials: Z
authors.lastname: Jiang