Details

Autor(en) / Beteiligte

• Belabbes, Abderrezak
• Bechstedt, Friedhelm

Titel

Forbidden Band‐Edge Excitons of Wurtzite‐GaP: A Theoretical View

Ist Teil von

• physica status solidi (b), 2019-02, Vol.256 (2), p.n/a

Erscheinungsjahr

2019

Link zum Volltext

Quelle

Wiley Online Library All Journals

Beschreibungen/Notizen

• By means of an approximate quasiparticle description we study the electronic structure of wurtzite‐GaP in more detail for the two lowest Γ8c and Γ7c conduction bands and the three highest Γ9v, Γ7+v, and Γ7−v valence bands. We conclude that the corresponding three gaps between the valence bands and the Γ8c conduction band are quasi‐direct, while the ones involving the s‐like Γ7c 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 Γ8c 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. Wurtzite‐GaP is a quasidirect semiconductor with a lowest conduction band of Γ8 symmetry. The corresponding optical transitions from the highest Γ9 and Γ7 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.