Index of content:
Volume 95, Issue 2, 15 January 2004
- DEVICE PHYSICS (PACS 85)
95(2004); http://dx.doi.org/10.1063/1.1627454View Description Hide Description
Electrical properties of rare-earth metal contacts on AlGaN/GaN heterostructure were interpreted in terms of the changes in microstructure and chemical bonding state. When the contacts were annealed under oxygen ambient at the Schottky barrier height increased from 0.56 to 1.10 eV for the Ru and from 0.68 to 1.07 eV for the Ir contact. Moreover, the reverse leakage current at dramatically reduced by 4 orders of magnitude by oxidationannealing. Such an improvement originated from the formation of and playing a key role in increasing the solubility of group-III atoms, namely, Ga and Al atoms. As a result, the surface Fermi level shifted toward the energy levels of group-III vacancies, resulting in the increase of Schottky barrier height. The electrical properties of heterostructure field effect transistor (HFET) applying the Ru gate contact significantly degraded when the device was annealed at under ambient. This was due to the indiffusion of the Ru atoms into the AlGaN layer during the oxidationannealing. However, no electrical degradation was found in the HFET using the Ir gate contact. The maximum drain current density of 714 mA/mm and transconductance of 171 mS/mm were kept even after annealing at
95(2004); http://dx.doi.org/10.1063/1.1634370View Description Hide Description
This article explores, through experiments and finite element analysis, the ability to plastically deformthin-filmsemiconductor structures on deformable substrates to spherical cap shapes without cracking the semiconductor layers. The major challenge involves contending with the large strain due to extreme deformation that will crack uniform stiff layers, such as silicon or silicon nitride. By patterning amorphous silicon and silicon nitride layers into islands, such problems can be avoided despite average strains in the substrate in excess of 5%. The strain in the device islands after deformation is a function of the island structure, size, and substrate material properties. Although the substrate is plastically expanded to a spherical dome, device islands can experience either tension or compression depending on the structure.
95(2004); http://dx.doi.org/10.1063/1.1633346View Description Hide Description
Hole phonon velocity in a strained Si inversion layer grown on a relaxed SiGe substrate has been theoretically investigated. We used: (i) a 20 band k.p Hamiltonian method for the valence-band structure calculation, (ii) a self-consistent Schrödinger and Poisson equations solver for the confined hole subband determination, (iii) a direct matrix Boltzmann transport equation solver including hole-phonon interactions for the carrier velocity estimation in the subband structure. The present work particularly focuses on the influence of SiGe alloy composition and strained Si layer thickness on the hole dynamic in the inversion layer. Our results highlight the linear slope of the hole velocity enhancement factor with strain in the Si layer. But at the same time, large strain facilitates transfer in the parasitic channel at the Si/SiGe interface for which the carrier mobility is highly degraded. Consequently, in order to optimize a p-channel transistor with Si layer strain on SiGe virtual substrate, a compromise must be found between mobility in Si layer and parasitic transfer phenomenon in this interface. Our results suggest that a 10 nm Si layer thickness strain on a relaxed allows one to take advantage of the strain-induced enhancements of carrier transport characteristics. At the same time this compromise is realistic from a technological point of view.