Valence-band ordering and magneto-optic exciton fine structure in ZnO

Abstract

Using first-principles linear muffin-tin orbital density functional band structure calculations, the ordering of the states in the wurtzite ZnO valence-band maximum, split by crystal-field and spin-orbit coupling effects, is found to be ⌫ 7(5) Ͼ⌫ 9(5) Ͼ⌫ 7(1) , in which the number in parentheses indicates the parent state without spin-orbit coupling. This results from the negative spin-orbit splitting, which in turn is due to the participation of the Zn 3d band. The result is found to be robust even when effects beyond the local density approximation on the Zn 3d band position are included. Using a Kohn-Luttinger model parametrized by our first-principles calculations, it is furthermore shown that the binding energies of the excitons primarily derived from each valence band differ by less than the valence-band splittings even when interband coupling effects are included. The binding energies of nϭ2 and nϭ1 excitons, however, are not in a simple 1/4 ratio. Our results are shown to be in good agreement with the recent magneto-optical experimental data by Reynolds et al. ͓Phys. Rev. B 60, 2340, in spite of the fact that on the basis of these data these authors claimed that the valence-band maximum would have ⌫ 9 symmetry. The differences between our and Reynolds' analysis of the data are discussed and arise from the sign of the Landé g factor for holes, which is here found to be negative for the upper ⌫ 7 band.

Efficient upconversion of photoluminescence via two-photon absorption in bulk and nanorod ZnO

“…states. Though these selections rules may be modified due to, e.g., strong admixture of dstates to the VB states that is the case for ZnO [34], the oscillator strength of TPA for the S excitons in bulk ZnO remains very low [32]. Our results show that the same selection rules also apply to nanostructured ZnO.…”

Valence band effective-mass Hamiltonians for the group-III nitrides from quasiparticle self-consistentGWband structures

“…This is well known to be also the case for ZnO. 38 In that case, the Zn-3d states are closer to the VBM. The value in GaN is already small due to the coupling with the Ga-3d and the small value of the N-2p atomic spin-orbit coupling which tend to compensate each other.…”

Electronic structure and optical properties ofZnX(X=O,S, Se, Te): A density functional study

“…the potential U ). Not only the band gap (E g ), but also the crystal-field (CF) and spin-orbit (SO) splitting energies (∆ CF and ∆ SO ), the order of states at the top of the valence band (VB), the location of the Zn-3d band and its width, and the band dispersion are found 21,22,26,27 to be incorrect for ZnO-w by the ab initio full potential (FP) and atomic-sphere-approximation (ASA) lin- ear muffin-tin orbital (LMTO) methods within the pure LDA, 26,27 and by the projector-augmented wave (PAW) method within LDA and GGA. 21,22 These findings were ascribed 21,22 to strong Coulomb correlation effects.…”

“…21,22 These findings were ascribed 21,22 to strong Coulomb correlation effects. DFT calculations within LDA plus self-interaction correction (LDA+SIC) and LDA+U are found 21,22,26 to rectify the errors related to ∆ CF and ∆ SO , order of states at the top VB, width and location of the Zn 3d band, as well as effective masses. In other semiconductors, in which the Coulomb correlation is not sufficiently strong, the ∆ CF and ∆ SO values derived from DFT calculations within LDA are found to be quite accurate.…”