Spectral response and field enhanced reverse current in a-Ge:H nip photodiodes

We demonstrate the effectiveness of using a high Ar+H₂ dilution of GeH₄, high pressure, and low substrate temperatures in producing device-grade a-Ge:H through standard radio-frequency glow discharge deposition. The enhanced plasma chemistry encourages the production, heating, and incorporation of nanoparticles to increase order, while the low substrate temperature encourages hydrogen incorporation to saturate dangling bonds. We utilize the material in nip photodiodes illuminated through the n-side, and demonstrate a device with an i-layer thickness of only 60 nm showing J_SC=20.6 mA/cm² (AM1.5 Efficiency=2.1%). Temperature-dependent conductivity and bias-dependent spectral response measurements suggest that a non-uniform field distribution and a defect-rich region near the i–p interface are currently the limiting factors for the device performance.     

Generalized nonlinear FET/HEMT modeling

A modeling procedure which provides an accurate large-signal response for variation in bias, input power level, and fundamental frequency for FET/HEMT transistors is designed. A procedure for measuring the large-signal input response on an easily implemented system is presented. The technique is illustrated by designing a nonlinear PHEMT model, which includes an accurate large-signal input response and works with variations in the aforementioned input conditions. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 122–133, 2004.     

Competitive motives and strategies: Understanding constructive competition.

This study examines the impact of motives and strategies on the constructiveness of competition. Sixty-four managers and 28 employees from Mainland China organizations described specific incidents of competition, from which indices of constructive competition were developed. They then rated motives and strategies that were hypothesized to affect competition and its outcomes. These indices of constructive competitive were then correlated with the motives and strategies. The results indicated that internal motivation to compete and the strategy of competing fairly were found to be the most powerful influences on the constructiveness of competition. Task and ego motives, extrinsic motivation, the motive to prevent others from benefiting, and the strategy to obstruct the other had very little impact on constructive competition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nanostructured virus crystals for X-ray optics

Certain virus structures can be assembled in the form of a periodic lattice with nanometer-range ordering. Cowpea mosaic virus is crystallized in body-centered-cubic geometry and used as a template for fabrication of metallized thin films with three-dimensional morphology. Calculations predict that these crystals exhibit a normal-incidence reflectivity of 7% for wavelengths around 35 nm, which can be utilized for soft X-ray optical systems.     

The students of the “systematic deviations from ordinary rectilineal construction” in the Athenian Parthenon

Certain small “systematic deviations from the straight line” were engineered by Athenian architects of the 5th c B.C. with the aim of attaining visual aesthetic excellence for certain sacred buildings on the Acropolis. Here, we describe more-or-less in chronological order, the work of the 18th and 19th c architects such as Stuart and Pennethorne who measured and then attempted to rationalise such deviations. Buildings where aesthetic appeal somewhat based on mathematics precedes fitness for structural function, are rare. This paper is to be read in conjunction with Ref. ^[1].     

Thin film transmission matrix approach to fourier transform infrared analysis of HgCdTe multilayer heterostructures

The ability to achieve high-yield focal plane arrays from Hg_1−xCd_xTe molecular beam epitaxy material depends strongly on postgrowth wafer analysis. Nondestructive analysis that can determine layer thicknesses as well as alloy compositions is critical in providing run-to-run consistency. In this paper, we incorporate the use of a thin film transmission matrix model to analyze Fourier transform infrared (FTIR) transmission spectra. Our model uses a genetic algorithm along with a multidimensional, nonlinear minimization Nelder-Mead algorithm to determine the composition and thickness of each layer in the measured epitaxial structure. Once a solution has been found, the software is able to predict detector performance such as quantum efficiency and spectral response. We have verified our model by comparing detector spectral data to our predicted spectral data derived from the room-temperature FTIR transmission data. Furthermore, the model can be used to generate design curves for detectors with varying absorber thicknesses and/or different operating temperatures. The consequence of this are reduced cycle times and reduced design variations.     

Reliability of large periphery GaN-on-Si HFETs

GaN devices exhibit excellent potential for use in many RF applications. However, commercial acceptance of the technology has been hindered by the scarcity and non-statistical nature of reliability results. In this work we present a full device level reliability study of GaN-on-Si HFETs. Reliability results on this technology include three-temperature DC data that show an activation energy of 1.7 eV and an average failure time >10⁷ h at 150 °C. Additionally, long duration DC lifetest (30 000 device hours) and RF lifetest (4000 device hours) results demonstrate a repeatable low drift process. Environmental tests such as autoclave and ESD demonstrate the ruggedness of the material system and technology. Finally, initial failure analysis is discussed.