Low multiplication noise thin Al0.6Ga0.4Asavalanche photodiodes

Avalanche multiplication and excess noise were measured on a series of Al_0.6Ga_0.4As p⁺in⁺ and n⁺ip⁺ diodes, with avalanche region thickness, w ranging from 0.026 μm to 0.85 μm. The results show that the ionization coefficient for electrons is slightly higher than for holes in thick, bulk material. At fixed multiplication values the excess noise factor was found to decrease with decreasing w, irrespective of injected carrier type. Owing to the wide Al_0.6Ga_0.4As bandgap extremely thin devices can sustain very high electric fields, giving rise to very low excess noise factors, of around F~3.3 at a multiplication factor of M~15.5 in the structure with w=0.026 μm. This is the lowest reported excess noise at this value of multiplication for devices grown on GaAs substrates. Recursion equation modeling, using both a hard threshold dead space model and one which incorporates the detailed history of the ionizing carriers, is used to model the nonlocal nature of impact ionization giving rise to the reduction in excess noise with decreasing w. Although the hard threshold dead space model could reproduce qualitatively the experimental results, better agreement was obtained from the history-dependent model     

Avalanche noise characteristics of thin GaAs structures withdistributed carrier generation [APDs]

It is known that both pure electron and pure hole injection into thin GaAs multiplication regions gives rise to avalanche multiplication with noise lower than predicted by the local noise model. In this paper, it is shown that the noise from multiplication initiated by carriers generated throughout a 0.1 μm avalanche region is also lower than predicted by the local model but higher than that obtained with pure injection of either carrier type. This behavior is due to the effects of nonlocal ionization brought about by the dead space; the minimum distance a carrier has to travel in the electric field to initiate an ionization event     

Effect of Silane-Functionalized RuO2 Nanoparticles on the Anticorrosive and Mechanical Properties of Poly (Methyl Methacrylate) Coatings

Metallurgical and Materials Transactions A - Newly synthesized poly (methyl methacrylate) (PMMA), silane, and nano ruthenium oxide (PMMA/silane/RuO2) nanocomposite coatings on Al alloy (AA7475) in...     

Interaction of CMC with video telecourses for distance education

There has been a significant increase in the distance learning programs at many academic and training centers. The growth has been stimulated by the availability of computers, satellites, and other telecommunication devices. A new era in education and training seems to be emerging.     

Solid-phase extraction of pesticides from water: possible interferences from dissolved organic material

A multiresidue analysis for trifluralin, simazine, atrazine, propazine, diazinon, parathion-methyl, alachlor, malathion, parathion, chlorpyrifos, pendimethalin, methidathion, and DEF in water that utilizes liquid-solid extraction (LSE) with octadecyl-bonded silica cartridges (C18BSCs) followed by gas chromatography/mass spectrometric analysis was developed. Recoveries of most pesticides were greater than 80% with C18BSCs from fortified water at concentration levels from about 1 to 500 ppb. Recoveries with C18BSCs, from an optically adjusted humic acid solution (10 ppm dissolved organic carbon) made to simulate a natural water with a high dissolved organic content, ranged from 29 to 153% and in general were lower than recoveries obtained from pure water. 14C-Labeled diazinon and parathion were recovered from the humic acid solution at levels of 57 and 68%, respectively, with C18BSCs; the remainder of the labeled pesticides was found in the cartridge eluents. Partition coefficients with human acid were calculated based on recovery of 14C-labeled pesticides from the C18BSCs.     

Separation of home intellectual environment and maternal IQ as determinants of child IQ.

Measured both parental and child IQs with the Raven Standard Progressive Matrices and the Peabody Picture Vocabulary Test; Ss included 80 mothers, 35 fathers, and 80 children (mean age 12 yrs). Home intellectual environment was assessed through a 2-hr interview with the mother. Multiple regression analyses showed that for each IQ test and for the 2 scores combined, the addition of home environment ratings to the regression equations did not add a significant increment to the prediction of child IQ from that provided by maternal IQ, whereas the addition of maternal IQ to the regression equation did add a significant increment to that provided by home environment ratings. Thus, the correlation of home environment and child IQ is considerably overestimated when maternal IQ is allowed to covary. When maternal IQ was statistically controlled, the correlation between home environment ratings and child IQ was attenuated to nonsignificance. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Low avalanche noise characteristics in thin InP p+-i-n+ diodes with electron initiated multiplication

We have performed electron initiated avalanche noise measurements on a range of homojunction InP p⁺-i-n⁺ diodes with “i” region widths, w ranging from 2.40 to 0.24 μm. In contrast to McIntyre's noise model a significant reduction in the excess noise factor is observed with decreasing w at a constant multiplication in spite of α, the electron ionization coefficient being less than β, the hole ionization coefficient. In the w=0.24 μm structure an effective β/α ratio of approximately 0.4 is deduced from the excess noise factor even when electrons initiate multiplication, suggesting that hole initiated multiplication is not always necessary for the lowest avalanche noise in InP-based avalanche photodiodes