Improved electronic structure and optical properties of sp-hybridized semiconductors using LDA+U SIC

Abstract

We propose the local density approximation (LDA) plus an on-site Coulomb self-interaction-like correction (SIC) potential for describing sp-hybridized bonds in semiconductors and insulators. We motivate the present LDA+U SIC scheme by comparing the exact exchange (EXX) hole with the LDA exchange hole. The LDA+U SIC method yields good band-gap energies E g and dielectric constants ε(ω≈ 0) of Si, Ge, GaAs, and ZnSe. We also show that LDA consistently underestimates the Γ-point effective electron m c and light-hole m lh masses, and the underlying reason for this is a too strong light-hole-electron coupling within LDA. The advantages of the LDA+U SIC approach are a computational time of the same order as the ordinary LDA, the orbital dependent LDA+U SIC exchange-correlation interaction is asymmetric analogously to the EXX potential, and the method can be used for materials and compounds involving localized d-and f -orbitals.

High absorption coefficients of the CuSb(Se,Te)2 and CuBi(S,Se)2 alloys enable high-efficient 100 nm thin-film photovoltaics

“…However, the effective electron masses at the CBM are relatively small for these compounds, for instance: m x ≈ 0. [23,24]). Interestingly, two of the mass components (m x and m z ) are similar for the two compounds, while the third compound (i.e., m y ) is significantly different.…”

“…A large k-mesh can be important to describe details in the absorption coefficient [21,22]. However, from test calculations we have found that the effect is not crucial for the considered materials, and we use HSE06 (which avoids incorrect resonance across the underestimated gaps for local potentials [23,24]) and with the same k-mesh as for the calculations of the LDOS.…”

Thin-film ZnO/CdS/CuIn1-xGa xSe2 solar cells: anomalous physical properties of the CuIn1-xGa xSe2 absorber

“…Thus, the band-gap energy of both CIS and CGS can be obtained from the similar SIC within LDA+U SIC . We have found [6] that effective masses and optical properties are somewhat overcompensated by fitting the LDA+U SIC band-gap energy to the exact experimental value. This can be a side effect of the energy-independent LDA+U SIC approach, but it can also be an indication that one may not be able to extract the experimental band-gap energy from the single-particle DFT/Kohn-Sham eigenvalues.…”

“…LDA fails to accurately describe this valence d-state localization in ZnO [9], where the LDA cation-anion 3d2p-hybridization disagrees with soft x-ray emission spectra. This shortcoming was corrected by the LDA+U SIC approach [6,9]:…”

“…The impacts due to doping and surface reconstruction on the PV device performance are discussed. The first-principles calculations are based on the local density approximation (LDA) within the density functional theory (DFT) with an on-site Coulomb selfinteraction-like correction (SIC) in the LDA+U SIC approach [6]. The defect transition and formation energies are obtained from total energies E(α, q) of defect α in charge state q, the chemical potentials µ α , and defect formation energies:…”