Forbidden Band‐Edge Excitons of Wurtzite‐GaP: A Theoretical View. Issue 2 (2nd August 2018)

• Record Type: Journal Article
• Authors: Belabbes, Abderrezak; Bechstedt, Friedhelm
• Other Names: Salvan Georgeta guestEditor.; Dzhagan Volodymyr guestEditor.; Vogt Patrick guestEditor.; Seyller Thomas guestEditor.
• Is Part Of: Physica status solidi. Volume 256:Issue 2(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2018-08-02
• Subjects: density functional theory (DFT) -- excitons -- gallium phosphide -- nanowires -- optical selection rules -- polarization dependence -- wurtzite; Solid state physics -- Periodicals; Solids -- Periodicals; Atomic structure -- Periodicals; 530.41
• DOI: 10.1002/pssb.201800238
• Languages: English
• ISSNs: 0370-1972

Abstract

Abstract : By means of an approximate quasiparticle description we study the electronic structure of wurtzite‐GaP in more detail for the two lowest Γ 8 c and Γ 7 c conduction bands and the three highest Γ 9 v, Γ 7 + v, and Γ 7 − v valence bands. We conclude that the corresponding three gaps between the valence bands and the Γ 8 c conduction band are quasi‐direct, while the ones involving the s ‐like Γ 7 c conduction band are direct. The optical oscillator strengths are also calculated outside the Γ point. Their influence on the observability of excitons in absorption and emission spectra is investigated. The almost dipole‐forbidden transitions into the lowest p ‐like Γ 8 c conduction band become substantial for finite wave vectors perpendicular to the c ‐axis. Therefore, the finite extent of the exciton envelope functions gives rise to non‐vanishing transition strengths, which explain the intense photoluminescence observed experimentally by forbidden p ‐type excitons. Abstract : Wurtzite‐GaP is a quasidirect semiconductor with a lowest conduction band of Γ 8 symmetry. The corresponding optical transitions from the highest Γ 9 and Γ 7 valence bands are almost forbidden at Γ . However, the optical matrix elements nearly increase linearly with the in‐plane wave vector. Consequently, the accompanying Wannier–Mott excitons with p character possess finite oscillator strengths, which explain the intense photoluminescence observed experimentally.