Conduction mechanisms and an evidence for phonon-assisted conduction process in thin high-k HfxTiySizO films
Abstract Electrical behavior of high-k Hf x Ti y Si z O layers with different Hf:Ti ratios in the film have been investigated. The films are prepared by MOCVD using novel single-source precursors chemistry. Oxide and interface charges, leakage currents and conduction mechanisms are found to be a strong function of the film composition. The films with lower Hf content show lower level of oxide and interface charges and higher dielectric constant whereas those with higher Hf content have better leakage current properties. It is established that in the films with lower Hf content the conduction is governed by a phonon-assisted process. The change of the conduction mechanism from Poole–Frenkel emission to phonon-assisted tunneling is assigned to possible structural changes which take place when changing the composition of the films.
Comparative Study of Flatband Voltage Transients on High-k Dielectric-Based Metal–Insulator–Semiconductor Capacitors
A systematic study of flatband voltage transients occurring in high-k dielectric-based metal-insulator-semiconductor structures has been carried out. Materials under study have been HfO 2 , HfSiO x , Gd 2 O 3 , Al 2 O 3 , and TiO 2 deposited on n-type silicon. At the flatband condition, in samples measured in darkness, under no electric fields and no field-related charge injection conditions, these transients are due to localized states in the insulator trapping electrons injected from the semiconductor by tunneling. The process is assisted by phonons and it is therefore thermally activated. Dependencies of the flatband voltage transients on the dielectric material, the bias history, and the hysteresis sign of the capacitance-voltage curves are demonstrated. The magnitudes of the flatband voltage transients clearly depend on the layer crystallinity; amorphous materials exhibit much lower transient amplitudes than crystalline or polycrystalline dielectrics.
Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy
Abstract We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2×10 13 to 2×10 17  cm −3 . We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Γ 0 increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.