Effect of impact ionization in the InGaAs absorber on excess noise of avalanche photodiodes

The effects of impact ionization in the InGaAs absorption layer on the multiplication, excess noise and breakdown voltage are modeled for avalanche photodiodes (APDs), both with InP and with InAlAs multiplication regions. The calculations allow for dead space effects and for the low field electron ionization observed in InGaAs. The results confirm that impact ionization in the InGaAs absorption layer increases the excess noise in InP APDs and that the effect imposes tight constraints on the doping of the charge control layer if avalanche noise is to be minimized. However, the excess noise of InAlAs APDs is predicted to be reduced by impact ionization in the InGaAs layer. Furthermore the breakdown voltage of InAlAs APDs is less sensitive to ionization in the InGaAs layer and these results increase tolerance to doping variations in the field control layer

Excess noise measurement in In0.53Ga0.47As

The excess noise due to impact ionization has been measured explicitly for the first time in In/sub 0.53/Ga/sub 0.47/As. By using a phase sensitive detection technique, the noise due to avalanche current was determined even in the presence of high tunneling currents. The excess noise due to pure electron injection measured on a series of thick In/sub 0.53/Ga/sub 0.47/As p/sup +/-i-n/sup +/ diodes suggests large electron to hole ionization coefficient ratio between 3.7 at electric field of 310 kV/spl middot/cm/sup -1/ to 5.3 at 260 kV/spl middot/cm/sup -1/. Excess noise was also measured at fields as low as 155 kV/spl middot/cm/sup -1/ suggesting that significant impact ionization occurs at these low fields. The multiplication and excess noise calculated using published ionization coefficients and ignoring dead space effects, gave good agreement with the experimental data for mixed and pure electron injection

Field dependence of impact ionization coefficients in In0.53Ga0.47As

Electron and hole ionization coefficients in In/sub 0.53/Ga/sub 0.47/As are deduced from mixed carrier avalanche photomultiplication measurements on a series of p-i-n diode layers, eliminating other effects that can lead to an increase in photocurrent with reverse bias. Low field ionization is observed for electrons but not for holes, resulting in a larger ratio of ionization coefficients, even at moderately high electric fields than previously reported. The measured ionization coefficients are marginally lower than those of GaAs for fields above 250 kVcm/sup -1/, supporting reports of slightly higher avalanche breakdown voltages in In/sub 0.53/Ga/sub 0.47/As than in GaAs p-i-n diodes

Consumer Perception of Sorghum Variety Attributes in the Lake Zone Tanzania

Many sorghum varieties have been developed by research institutes in an effort to address food security problems in the semi-arid areas of Tanzania. Although sorghum is better adapted to drier areas than maize, farmer adoption rates for sorghum varieties are always lower than that of maize. In addition, maize based food is more acceptable to urban consumers than sorghum based food. In this study consumer evaluated quality attributes of sorghum ugali based on different varieties in order to determine marketing potential relating to the different improved sorghum varieties. A total of 231 consumers, randomly selected from urban and rural areas participated in a food panel to evaluate ugali prepared from five sorghum varieties (three improved, two local). Conjoint analysis was used to determine consumer perceptions of the variety attributes, while a logistic model was applied to determine preference ranking of different varieties. The results indicated that the color and taste of sorghum ugali were the most important criteria used by consumers to evaluate the quality ugali. The study results indicated that sorghum ugali with white/khaki color and the majority of panel participants preferred neutral or slightly sweet taste. Consumers from rural and urban areas accepted two improved varieties; only consumers from rural areas accepted the remaining variety.Adoption, consumer perception, conjoint analysis, sorghum varieties, Tanzania, Agricultural and Food Policy, Consumer/Household Economics, Demand and Price Analysis, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, Marketing, Productivity Analysis, Research and Development/Tech Change/Emerging Technologies,

Optimization of InP APDs for high-speed lightwave systems

Calculations based on a rigorous analytical model are carried out to optimize the width of the indium phosphide avalanche region in high-speed direct-detection avalanche photodiode-based optical receivers. The model includes the effects of intersymbol interference (ISI), tunneling current, avalanche noise, and its correlation with the stochastic avalanche duration, as well as dead space. A minimum receiver sensitivity of -28 dBm is predicted at an optimal width of 0.18 mu m and an optimal gain of approximately 13, for a 10 Gb/s communication system, assuming a Johnson noise level of 629 noise electrons per bit. The interplay among the factors controlling the optimum sensitivity is confirmed. Results show that for a given transmission speed, as the device width decreases below an optimum value, increased tunneling current outweighs avalanche noise reduction due to dead space, resulting in an increase in receiver sensitivity. As the device width increases above its optimum value, the receiver sensitivity increases as device bandwidth decreases, causing ISI to dominate avalanche noise and tunneling current shot noise

The Worst System of Citation Except for All the Others

Now in its twentieth edition, The Bluebook continues to cast its shadow over the legal profession just as it has for almost 100 years, helping legal writers format their references to authorities in briefs, memoranda, opinions, and law review articles. Previous critiques have offered various theories for why, despite its problems, The Bluebook remains the standard for legal citation. Ivy League elitism, the first-mover advantage, and lawyers’ conservative preference for the status quo have all been offered to explain the seemingly inexplicable: If this system is so terrible, then why are we still stuck with it? One potential answer to that question has remained largely unexplored by previous scholarship, because previous scholarship has accepted the question’s underlying premise. This essay challenges that premise by offering a novel explanation for The Bluebook’s continued existence: Perhaps The Bluebook survives because it’s not so terrible after all.Perhaps The Bluebook works quite well for the task it was designed to perform. Part I begins with an examination of The Bluebook’s primary task: providing citation rules for student-run law journals. Previous authors have noted that The Bluebook’s rules provide the benefit of certainty that comes with clear answers to citation questions, even if obtaining that certainty takes a bit of work. Part I argues that, in the context of student-run law journals with dozens of editors collectively working on dozens of separate articles over a two-year period, this rule-based certainty also increases efficiency, even if individual editors initially waste time looking up picayune rules. Adopting a looser, standard-based system of citation might actually increase the time wasted by journal editors on footnote revisions. Part II explains how The Bluebook’s two-part structure—the Whitepages for journal editors and the Bluepages for practitioners—allows flexibility for practitioners, if that’s what a practitioner wants. This selective flexibility allows The Bluebook to continue to serve lawyers even after they’ve left law school. Part II also addresses some practice-based criticisms of The Bluebook and explains how these criticisms both understate the benefits of The Bluebook’s rules and vastly overstate the benefits of alternative systems based on loose standards. Even The Bluebook’s harshest critics, such as Judge Richard Posner, rely on The Bluebook’s system of rules much more than they like to admit. Part III then looks into the future, through the lens of The Bluebook’s newest competitor: The Indigo Book, a freely available, open-source expression of The Bluebook’s system of citation. As a static publication, The Indigo Book breaks no new ground. But as a continuing project, The Indigo Book might be revolutionary, since the project seeks to wrest control of legal citation from Ivy League law students and give it back to you, the people. What does this mean for The Bluebook and legal citation in the coming decade? Part III engages in wild speculation. Thanks to The Indigo Book, the law’s citation rules may become a free, open, and collaboratively edited system—much like Wikipedia. Part III concludes by suggesting that, also like Wikipedia, this new online system may have benefits, but it may also grow more complicated and labyrinthine than its student-created counterpart

Citation, Slavery, and the Law as Choice: Thoughts on Bluebook Rule 10.7.1(d)

Today, more than 150 years after the end of the Civil War, lawyers and judges continue to rely on antebellum decisions that tacitly or expressly approve of slavery. This reliance often occurs without any acknowledgement of the precedent’s immoral and legally dubious provenance. Modern use of these so-called “slave cases” was the subject of Professor Justin Simard’s 2020 article, Citing Slavery. In response to Professor Simard’s article, the latest edition of The Bluebook includes Rule 10.7.1(d), which requires authors to indicate parenthetically when a decision involves an enslaved person as a party or the property at issue. Unfortunately, Rule 10.7.1(d) applies only to academic writing—journal articles authored by law professors and students. It therefore does not address the moral and dignitary harms that result from courts’ and lawyers’ use of slave cases to invoke the legal force of the state. Courts themselves, therefore, must decide whether to require a parenthetical for slave cases. As it should be. Courts, not a student-written style guide, are responsible for addressing the judiciary’s connection to slavery. That responsibility counsels in favor of adopting Rule 10.7.1(d) as a tool to prompt lawyers and judges to carefully consider—and perhaps forgo—continued reliance on slave cases

Absorption coefficients in AlGaInP lattice-matched to GaAs

The absorption coefficient of AlGaInP lattice-matched to GaAs, across the composition range from AlInP to GaInP has been obtained from photocurrent versus wavelength measurements on seven homo-junction AlGaInP PIN diode structures. Due to the sensitivity of the photocurrent measurement technique, values of absorption down to 100 cm−1 have been determined close to the band-gap. From these, the bandgaps in this material system were extracted across the composition range and these corroborate data in the literature that shows the band-gap becoming indirect when the aluminium content, x>0.48

A theoretical comparison of the breakdown behavior of In0.52Al0.48As and InP near-infrared single-photon avalanche photodiodes

We study the breakdown characteristics and timing statistics of InP and In0.52Al0.48As single-photon avalanche photodiodes (SPADs) with avalanche widths ranging from 0.2 to 1.0 mu m at room temperature using a random ionization path-length model. Our results show that, for a given avalanche width, the breakdown probability of In0.52Al0.48As SPADs increases faster with overbias than InP SPADs. When we compared their timing statistics, we observed that, for a given breakdown probability, InP requires a shorter time to reach breakdown and exhibits a smaller timing jitter than In0.52Al0.48As. However, due to the lower dark count probability and faster rise in breakdown probability with overbias, In0.52Al0.48As SPADs with avalanche widths <= 0.5 mu m are more suitable for single-photon detection at telecommunication wavelengths than InP SPADs. Moreover, we predict that, in InP SPADs with avalanche widths <= 0.3 mu m and In0.52Al0.48As SPADs with avalanche widths <= 0.2 mu m, the dark count probability is higher than the photon count probability for all applied biases