physica status solidi (RRL) - Rapid Research Letters · 2010 · 29 citations · 6 references
Natural SciencesMaterials EngineeringMaterials ScienceOptical MaterialsOptoelectronicsThin FilmsDopingOptical Thin FilmsOxide SemiconductorsThin Film Electrical PropertiesThin Film Optical PropertiesThin-film MaterialsCarrier ConcentrationConduction BandFermi LevelMolecular Beam EpitaxyOptical TransparencyThermal ActivationTransparencyZinc Oxides
Abstract We demonstrate a critical effect of a metal‐to‐oxygen ratio on the electrical, optical, and structural properties of ZnO films heavily doped with Ga (carrier concentration in the range of 10 20 –10 21 cm –3 ) grown by plasma‐assisted molecular beam epitaxy. The as‐grown layers prepared under the metal‐rich conditions exhibited resistivities below 3 × 10 –4 Ω cm and an optical transparency exceeding 90% in the visible spectral range as well as a large blue shift of the transmission/absorption edge attributed to the Burstein–Moss shift of the Fermi level deep into the conduction band, indicating high donor concentration. In contrast, the films grown under the oxygen‐rich conditions required thermal activation and showed inferior properties. Furthermore, electrical measurements point to the nonuniform depth distribution of free carriers. An oxygen‐pressure‐dependent surface disordering is suggested to be responsible for the drastic effect of the metal‐to‐oxygen ratio on the film properties. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
6
Ga-doped ZnO films grown on GaN templates by plasma-assisted molecular-beam epitaxy
Han Jong Ko, Y. F. Chen, Soon‐Ku Hong et al. · Applied Physics Letters · 2000 · 371 citations