TY - JOUR
T1 - Structural, electrical, and optical properties of hydrogen-doped ZnO films
AU - Kronenberger, Achim
AU - Polity, Angelika
AU - Hofmann, Detlev M.
AU - Meyer, Bruno K.
AU - Schleife, André
AU - Bechstedt, Friedhelm
PY - 2012/9/28
Y1 - 2012/9/28
N2 - Hydrogen doped ZnO thin films were deposited by radio frequency magnetron sputtering from a ceramic target on c-plane sapphire and fused silica using H 2 and O 2 as reactive gases. Structural analysis revealed that all films are polycrystalline with the c axis oriented perpendicularly to the substrate surface. The lateral grain size was strongly affected by the oxygen content of the sputtering gas and decreased dramatically above a critical content of 4.5%. We were able to adjust the carrier density of the films by the deposition parameters to any value between 1014 and 2×1020 cm -3. Using temperature-dependent Hall-effect measurements we identified thermionic emission over Coulomb-barriers created by surface trap states at the grain boundaries and tunneling effects to dominate the carrier transport. Preparing and thoroughly characterizing the films is a prerequisite for our investigation of the dependence of the optical band gap energy on the carrier density. We use results from experiment as well as first-principles calculations (including Burstein-Moss shift, band gap renormalization, and excitonic effects) in order to understand the mechanisms that determine how free electrons influence the energy position of the optical absorption onset.
AB - Hydrogen doped ZnO thin films were deposited by radio frequency magnetron sputtering from a ceramic target on c-plane sapphire and fused silica using H 2 and O 2 as reactive gases. Structural analysis revealed that all films are polycrystalline with the c axis oriented perpendicularly to the substrate surface. The lateral grain size was strongly affected by the oxygen content of the sputtering gas and decreased dramatically above a critical content of 4.5%. We were able to adjust the carrier density of the films by the deposition parameters to any value between 1014 and 2×1020 cm -3. Using temperature-dependent Hall-effect measurements we identified thermionic emission over Coulomb-barriers created by surface trap states at the grain boundaries and tunneling effects to dominate the carrier transport. Preparing and thoroughly characterizing the films is a prerequisite for our investigation of the dependence of the optical band gap energy on the carrier density. We use results from experiment as well as first-principles calculations (including Burstein-Moss shift, band gap renormalization, and excitonic effects) in order to understand the mechanisms that determine how free electrons influence the energy position of the optical absorption onset.
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U2 - 10.1103/PhysRevB.86.115334
DO - 10.1103/PhysRevB.86.115334
M3 - Article
AN - SCOPUS:84866976172
SN - 1098-0121
VL - 86
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
IS - 11
M1 - 115334
ER -