Fabrication Of Functional Devices Research Articles

Low-resistance Ohmic Contacts to N-face p-GaN for the Fabrication of Functional Devices

AbstractThe electrical properties of Ni-based ohmic contacts N-face p-type GaN are presented. The specific contact resistance of N-face p-GaN exhibits a liner decrease from 1.01 × cm2 to 9.05 × 10-3 Ω cm2 for the as-deposited and the annealed Ni/Au contacts, respectively, with increasing annealing temperature Furthermore, the specific contact resistance could be decreased by four orders of magnitude to 1.03 × 10-4 Ω cm2 as a result of surface treatment using an alcohol-based (NH4)2S solution. The depth profile data measured by the intensity of O1s core peak in the x-ray photoemission spectra showed that the alcohol-based (NH4)2S treatment was effective in removing of the surface oxide layer of GaN. In addition, a Ga 2p core-level peak showed a red-shift of binding energy by 0.3 eV by alcohol-based (NH4)2S treatment, indicating that the surface Fermi level was shifted toward the valence-band edge. Thus, the low ohmic contact behavior observed in our treated sample might be explained in terms of the removal of the oxide layer and reducing the barrier heights by reduced band-bending effect.

Interface engineering for Ge metal-oxide–semiconductor devices

High mobility semiconductors such as Ge with high- k gates may be required to enhance performance of future devices. One of the biggest challenges for the development of a Ge metal-oxide–semiconductor (MOS) technology is to find appropriate passivating materials and methodologies for the Ge/high- k interfaces. Germanium oxynitride is frequently used as a passivating interlayer in combination with HfO 2 and is found to be necessary for the fabrication of functional devices. However, it is also considered to be insufficient since electrical characteristics in capacitors are non-ideal and field effect transistors underperform, probably due to a the high density of interface defects. We show that alternative passivating rare earth oxide layers prepared by molecular beam deposition produce improved electrical characteristics and a significant reduction of the density of interface states. In the case of CeO 2, a thick interfacial layer is spontaneously formed containing oxidized Ge, which is considered to be the key for the observed improvements.

Rare earth oxides as high-k dielectrics for Ge based MOS devices: An electrical study of Pt/Gd2O3/Ge capacitors

Germanium technology aiming at the fabrication of functional devices strongly depends on the electrical behaviour of both the oxide bulk and the oxide/Ge interface. Field effect transistors underperform and express non ideal characteristics due to high values of interface defects in conjunction with bulk states. In this paper, we show that rare earth oxide layers of Gd2O3 prepared by molecular beam deposition on Ge substrates produce improved insulating characteristics. The current density at 1V was as low as J=50nA/cm2. The calculated value of the dielectric constant was around 10 and an EOT value equal to 3.7nm was obtained, while the density of the interface states was approximately 2×1012cm−2eV−1. A detailed analysis of the electrical measurements of MOS capacitors revealed the existence of bulk electron traps in the semiconductor which need special attention if rare earth oxides are to be used in Ge based MOS devices.

Fabrication of Functional Devices Based on Highly Ordered Anodic Porous Alumina

Fabrication of Functional Devices Based on Highly Ordered Anodic Porous Alumina

Nanoscale Control of Layer Thickness for EL Devices by Mass-controlled Layer-by-layer Sequential Adsorption Process

ABSTRACTA mass controlled layer-by-layer sequenitial adsorption process for polyelectlrolytes was newly developed for the fabrication of functional devices using ultra-thin organic film formed by various polymers of different polarity of charge. In this study hydrophobic Ruthenium complex monomer • tris(bipyridyl) ruthenium(II) hexafluorophosphate • was micelle-wrapped with an anionic surfactant, sodium dodecylbenzenesulfonate, and was assembled with PAH (poly (allylamine hydrochloride)), which has the opposite charge, on ITO substrates. With this method, we succeeded in fabricating ultra-thin organic films even when the adsorption material is not polymer but monomer. Moreover it was found that the film thickness of the self-assembled Ru micelle/PAH had a linear relationship with the number of bilayers. By using this process, an EL device was fabricated by depositing the thin film of micelle-wrapping ruthenium complex monomer on ITO and metal electrode on top of the film. Light emission was observed by applying voltage to this device.