Temperature dependence of the Fermi level in low-temperature-grown GaAs

Highly resistive molecular beam epitaxial GaN layers are characterized by temperature dependent conductivity and Hall effect measurements. Seven n-type GaN samples with room temperature layer resistivity ranging between 8 and 4.2ϫ10 6 ⍀ cm are used in this study. The experimental data are analyzed by considering various transport models such as band and hopping conduction, scattering on charged dislocations and grain boundaries controlled transport. The same defect level of 0.23 eV, attributed to nitrogen vacancy, is found for layers with 300 р3.7ϫ10 3 ⍀ cm. The Hall mobility for two lower resistivity layers is influenced mainly by phonon scattering (H ϳT x , xϭϪ1.4). However, higher resistivity layers show positive mobility power, xϭ0.5-0.9, which can be explained by dominating scattering on charged dislocations. Properties of layers with the highest resistivity ͑1ϫ10 5 and 4.2ϫ10 6 ⍀ cm͒ and extremely low Hall mobility ͑6 and Ͻ0.1 cm 2 V Ϫ1 s Ϫ1 ͒ are consistent with grain boundary controlled transport. The barrier height between grains of 0.11 eV and an average grain size of 200 nm are found. Neither nearest-neighbor or variable range single phonon hopping nor multiphonon hopping can be clearly attributed to the conduction of the layers investigated.

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“…Its conduction at room temperature is mainly by hopping among defect centers 21 and the estimated width of the defect band is about 0.15 eV. 22…”

Section: B Band Conductionmentioning

confidence: 99%

Conductivity and Hall effect characterization of highly resistive molecular-beam epitaxial GaN layers

Kordoš¹,

Morvič

Betko

et al. 2000

Journal of Applied Physics

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“…A the deep level in high concentration can pin the Fermi level, as was assumed for the as-grown semi-insulating GaAs. [39][40][41] In the following analysis the deep level will be considered as acceptor-type. This assumption was suggested by a recent report on the presence of negative charges at the surface of ferroelectric films.…”

Section: Metal-ferroelectric Interfacementioning

confidence: 99%

Metal-ferroelectric-metal heterostructures with Schottky contacts. I. Influence of the ferroelectric properties

Pintilie

Alexe

2005

Journal of Applied Physics

269

184

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A model for Metal-Ferroelectric-Metal structures with Schottky contacts is proposed. The model adapts the general theories of metal-semiconductor rectifying contacts for the particular case of metal-ferroelectric contact by introducing: the ferroelectric polarization as a sheet of surface charge located at a finite distance from the electrode interface; a deep trapping level of high concentration; the static and dynamic values of the dielectric constant. Consequences of the proposed model on relevant quantities of the Schottky contact such as built-in voltage, charge density and depletion width, as well as on the interpretation of the current-voltage and capacitance-voltage characteristics are discussed in detail.

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“…This is exactly what we obtain with a Fermi level under the top half part of the defect band with the condition (ε F − ε C ) < W/2. The defect bandwidth is found to be in the same range as those (150-250 meV) extracted from spectroscopic measurements performed on thick GaAs layers [61,62].…”

Section: Research Of Highly Spin-polarized Sourcementioning

confidence: 81%