Energy spectrum of near-edge holes and conduction mechanisms in Cu2ZnSiSe4 single crystals

• Published in: Journal of alloys and compounds 2013-12, Vol.580, p.481-486
• Main Authors: Lisunov, K.G., Guc, M., Levcenko, S., Dumcenco, D., Huang, Y.S., Gurieva, G., Schorr, S., Arushanov, E.
• Format: Article
• Language: English
• Subjects: Alloys; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Conductivity phenomena in semiconductors and insulators; Density; Density of states; Electrical resistivity; Electrical transport; Electron states; Electronic properties; Electronic transport in condensed matter; Exact sciences and technology; Excitation spectra; Fermi surface: calculations and measurements; effective mass, g factor; Metal-insulator transition; Metal-insulator transitions and other electronic transitions; Methods of electronic structure calculations; Mobility edges; hopping transport; Optical materials; Physics; Semiconductors; Single crystals; Valence band
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2013.06.156

•Resistivity of single crystalline p-Cu2ZnSiSe4 is investigated between 10 and 300K.•Variable-range hopping conduction of the Mott type is established below ∼200K.•Conductivity connected to the activation of holes is observed between ∼200 and 300K.•Width and density of the localized states of the acceptor band are determined.•Localization radii and Bohr radius of the localized carriers are obtained. A model of the energy spectrum of holes near the edge of the valence band of Cu2ZnSiSe4 is proposed from investigations of the resistivity, ρ(T), in Cu2ZnSiSe4 single crystals. The Mott variable-range hopping (VRH) conductivity mechanism is established in the temperature interval of ∼100–200K, whereas between ∼200 and 300K, the conductivity is determined by thermal excitations of holes to the mobility edge of the joint energy spectrum of the overlapped acceptor and valence bands. Parameters of the localized holes and details of the density of states near the edge of the valence band are determined, including the relative acceptor concentration, N/Nc≈0.41–0.49 (where Nc≈7×1018cm−3 is the critical concentration of the metal–insulator transition), the relative localization radius a/aB≈1.7–2.1 (where aB≈13.1Å is the Bohr radius), the semi-width of the acceptor band, W≈95–106meV, centered at the energy E0≈59meV above the top of the valence band, the average density of the localized states (DOS), gav∼(1.4–1.8)×1016meV−1cm−3 and the DOS at the Fermi level, g(μ)≈(4.1–5.4)×1015meV−1cm−3.