Fermi-level band filling and band-gap renormalization in Ga-doped ZnO

摘要

The fundamental optical properties of Ga-doped ZnO films grown by metalorganic chemical vapor deposition were investigated by room-temperature transmittance and photoluminescence (PL) spectroscopy. The Burstein-Moss (BM) shift of the absorption edge energy is observed at the carrier concentration up to 2.47 X 10~(19) cm~(-3). The absorption edges are fitted to a comprehensive model based on the electronic energy-band structure near critical points plus relevant discrete and continuum excitonic effects, taking account of the Fermi-level filling factor. The theoretical calculation for BM effect is in good agreement with the experimental facts, considering the nonparabolic nature of conduction-band and band-gap renormalization (BGR) effects. Meanwhile, the monotonic redshift of the near-band-gap emission detected by PL measurements has also been observed with increasing free-carrier concentration, which is attributed to the BGR effects, and can be fitted by an n~(1/3) power law with a BGR coefficient of 1.3 X 10~(-50) meV cm.