Linear Programming Relaxations of Quadratically Constrained Quadratic Programs

We investigate the use of linear programming tools for solving semidefinite programming relaxations of quadratically constrained quadratic problems. Classes of valid linear inequalities are presented, including sparse PSD cuts, and principal minors PSD cuts. Computational results based on instances from the literature are presented.Comment: Published in IMA Volumes in Mathematics and its Applications, 2012, Volume 15

Calibration of an optoelectronic system for the characteristion of ultraviolet sensitive photodiodes

Spectral and electrical characteristion of ultraviolet (UV) sensitive photodiodes requires a calibrated optoelectronic system. For spectral characteristion, the irradiance of the UV light source, after the light passed through a monochromator and optical fiber, was calibrated for wavelengths ranging from 200 nm to 400 nm. Commercially available AlGaN-based photodiodes was characterised and the obtained parameters were compared to that specified.http://www.satnt.ac.z

Electrical characterization of defects introduced in n-Ge during electron beam deposition or exposure

Schottky barrier diodes prepared by electron beam deposition (EBD) on Sb-doped n-type Ge were characterized using deep level transient spectroscopy (DLTS). Pt EBD diodes manufactured with forming gas in the chamber had two defects, E0.28 and E0.31, which were not previously observed after EBD. By shielding the samples mechanically during EBD, superior diodes were produced with no measureable deep levels, establishing that energetic ions created in the electron beam path were responsible for the majority of defects observed in the unshielded sample. Ge samples that were first exposed to the conditions of EBD, without metal deposition (called electron beam exposure herein), introduced a number of new defects not seen after EBD with only the E-center being common to both processes. Substantial differences were noted when these DLTS spectra were compared to those obtained using diodes irradiated by MeV electrons or alpha particles indicating that very different defect creation mechanisms are at play when too little energy is available to form Frenkel pairs. These observations suggest that when EBD ions and energetic particles collide with the sample surface, inducing intrinsic non-localised lattice excitations, they modify defects deeper in the semiconductor thus rendering them observable.The South African National Research Foundationhttp://jap.aip.org/am201

The effect of alpha particle irradiation on electrical properties and defects of ZnO thin films prepared by sol-gel spin coating

Please read abstract in the article.The National Research Foundation of South Africa (NRF)http://www.elsevier.com/locate/mssp2020-10-01hj2020Physic

Current-voltage temperature characteristics of Au/n-Ge (1 0 0) Schottky diodes

The variation in electrical characteristics of Au/n-Ge (1 0 0) Schottky contacts have been systematically investigated as a function of temperature using current-voltage (I-V) measurements in the temperature range 140-300 K. The I-V characteristics of the diodes indicate very strong temperature dependence. While the ideality factor n decreases, the zero-bias Schottky barrier height (SBH) ( ɸʙ) increases with the increasing temperature. The I-V characteristics are analysed using the thermionic emission (TE) model and the assumption of a Gaussian distribution of the barrier heights ɸʙ vs. ½ kT plot has been used to show the evidence of a Gaussian distribution of barrier heights and values of ɸʙ = 0.615 eV and standard deviation σs0 = 0.00858 eV for the mean barrier height and zero-bias standard deviation have been obtained from this plot, respectively. The Richardson constant and the mean barrier height from the modified Richardson plot were obtained as 1.37 A cm-2 K-2 and 0.639 eV, respectively. This Richardson constant is much smaller than the reported of 50 A cm-2 K-2. This may be due to greater inhomogeneities at the interface.The South African National Research Foundationhttp://www.elsevier.com/locate/physbnf201

Electrical characterisation of ruthenium Schottky contacts on n-Ge (1 0 0)

Please read abstract in the article.The South African National Research Foundationhttp://www.elsevier.com/locate/physbnf201

Determination of the laterally homogeneous barrier height of palladium Schottky barrier diodes on n-Ge (1 1 1)

We have studied the experimental linear relationship between barrier heights and ideality factors for palladium (Pd) on bulk-grown (1 1 1) Sb-doped n-type germanium (Ge) metal-semiconductor structures with a doping density of about 2.5×1015 cm−3. The Pd Schottky contacts were fabricated by vacuum resistive evaporation. The electrical analysis of the contacts was investigated by means of current–voltage (I–V) and capacitance–voltage (C–V) measurements at a temperature of 296 K. The effective barrier heights from I–V characteristics varied from 0.492 to 0.550 eV, the ideality factor n varied from 1.140 to 1.950, and from reverse bias capacitance–voltage (C−2–V) characteristics the barrier height varied from 0.427 to 0.509 eV. The lateral homogenous barrier height value of 0.558 eV for the contacts was obtained from the linear relationship between experimental barrier heights and ideality factors. Furthermore the experimental barrier height distribution obtained from I–V and (C−2−V) characteristics were fitted by Gaussian distribution function, and their mean values were found to be 0.529 and 0.463 eV, respectively

Defects in swift heavy ion irradiated n-4H-SiC

Please read abstract in the article.http://www.elsevier.com/locate/nimb2020-12-01hj2020Physic

Defects induced by solid state reactions at the tungsten-silicon carbide interface

Defects introduced by the solid state reactions between tungsten and silicon carbide have been studied using deep level transient spectroscopy (DLTS) and Laplace DLTS. W/4H-SiC Schottky barrier diodes were isochronally annealed in the 100–1100 C temperature range. Phase composition transitions and the associated evolution in the surface morphology were investigated using x-ray diffraction (XRD) and scanning electron microscopy (SEM). After annealing at 1100 C, the E0.08, E0.15, E0.23, E0.34, E0.35, E0.61, E0.67, and E0.82 defects were observed. Our study reveals that products of thermal reactions at the interface between tungsten and n-4H-SiC may migrate into the semiconductor, resulting in electrically active defect states in the bandgap.The South African National Research Foundation (NRF) and the University of Pretoria.http://aip.scitation.org/journal/jap2019-01-18am2018Physic