Modeling and Characterization of Efficient Carrier Multiplication in Highly Co-doped Semiconductors and Disordered Materials

This thesis offers modeling of a newly discovered gain mechanism for various photodetection applications. Conventional avalanche photodetectors have been in use for the past four decades with impact ionization being the underlying carrier multiplication mechanism.However, tradeoff between sensitivity, dynamic range and bandwidth are some of the drawbacks of the present day photodetection technology. The newly discovered cycling excitation process (CEP) can be a potential candidate to address these issues with linear photo response, single photon sensitivity and high gain bandwidth product. The key feature of CEP is introduction of counter dopants in p-n junction silicon diode, with which the efficiency of auger excitation can be enhanced to great extent by facilitating relaxation of k selection rule. Higher uncertainty in k spaces dictates localization of carriers in real space. Hence, an initial hot carrier can excite electron-hole pair between localized states (e.g. from states closer to valence band to states closer to conduction band) at much lower bias. Another essential component of CEP is phonon/field assisted tunneling from localized states to mobile bands. Contrary to other photodetectors, phonons, actually, play a positive role in achieving gain. Experimentally gain of ~4000 at only 4V have been achieved in the CEP test structure along with photo response dependence on input light power, which is helpful for photon number resolving. Temperature dependent measurement also shows the positive role of phonons. Density functional theory calculation shows the change in band structure with doping bulk crystalline silicon with boron (B) and phosphorous (P) simultaneously. Comparison of density of states exhibits existence of states inside band gap. Furthermore, charge density plot clearly demonstrates electron and hole localization centered around P and B atoms respectively. Hence, highly counter doping with BP atoms turns the crystalline silicon into a quasi-disordered material. Since, highly counter doping introduces disorder in silicon, with this notion naturally disordered materials are explored as possible CEP gain media. Amorphous materials have low mobility due to their nature of disorder. Surprisingly, amorphous silicon (a-Si) photodiodes with thin a-Si layer (~40nm) have shown a gain-bandwidth product of over 2 THz with very low excess noise. To unveil the true gain mechanism, the thesis further delves into theoretical modeling and numerical analysis along with experimental data at different frequencies. Evidence of highly effective carrier multiplication process within a-Si as the primary gain mechanism, especially at high frequency is shown. There is also trap-induced junction modulation at much lower frequency. The analysis further suggests that the carrier multiplication process in thin a-Si can be much more efficient than in thick a-Si, even stronger than single crystalline Si in some cases. Although seemingly counter intuitive, this is consistent with the proposed cycling excitation process (CEP) where the localized states in the bandtails of disordered materials such as a-Si relax the k-selection rule and increase the rate of carrier multiplication. A more rigorous quantum mechanical scattering rate calculation also demonstrates the increase of strength of carrier multiplication with the presence of localized states and the increase of ionization coefficient with decreasing thickness of gain medium. A theoretical framework is offered to calculate the carrier multiplication process in a-Si or other disordered materials involving donor acceptor pairs (DAPs) and to answer several key and seemingly counter intuitive questions such as why amorphous silicon can be more efficient carrier multiplication material than single crystal silicon, why low carrier mobility of amorphous material helps rather than hurt carrier multiplication process, and why thin a-Si is more efficient than thick a-Si in carrier multiplication

The Impact Of Exchange Rate Misalignment And Volatility On Malaysian Trade Flows

This study empirically examines the influence of real exchange rate behaviors, explicitly in term of its misalignment and volatility on the trade flows of a small fastgrowing economy, particularly Malaysia by employing Johansen multivariate errorcorrection model as well as autoregressive distributed lag (ARDL) to capture the estimates of the long-run and short-run relationships over the quarterly data for the period of 1991:1 to 2003:4. A measure of the quantitative proxy of the real exchange rate misalignment is constructed through the NATREX model while the volatility of real exchange rate is generated from the GARCH (1,1) model. It is particularly crucial because international trade played as main engine to generate and sustain economic growth for small open economies. A number of important conclusions can be drawn from the study. It is observed that the Malaysian real exchange rate was overvalued before the eruption of the Asian financial crisis in 1993-1997. After the crisis, the rate was undervalued in the mid 1997-2003. The rate was stable prior to the crisis, but was very volatile during the crisis period. The empirical finding shows that the Malaysia’s exports and imports are more sensitive to exchange rate misalignment throughout the sample-study period. In the meantime, exchange rate volatility appears to be most harmful to the Malaysia’s exports and imports in the post-sample period during the 1997 Asian financial crisis. On the other hand, the income effect provide a conducive condition to further boost Malaysia’s exports and imports as increase in the foreign and domestic income, respectively. For the price effect, Malaysia seems to offer a competitive price of export in pre-crisis period while Malaysia’s import is price inelastic through the sample period, where as a small open economy, Malaysia acts as a price taker in the international market. Nevertheless, the shift to a fixed or pegged exchange rate system is an appropriate measure as it reduced magnitude of the exchange rate misalignment and volatility (as computed through ATSSE and ATSCSD, respectively), where it may seem to be a successful case of crisis management in a small open dynamic economy, namely Malaysia

Economic Revolution Of This Century

I have developed a new financial instrument which will be much more valuable than the bonds or the treasury bills government sells in the open market to raise much needed funds to run the country. These are all interest based instruments and can only be used by institutions. The instrument I am proposing is without interest and will be used by everybody to purchased goods and services in the government and private sector resulting in up to 60% discounts .This is why these will be massively bought up front in large amounts in the shortest period of time of one month to run the country for at least a year and much more by the end of the year. INTRODUCTION: The world is facing many challenges with no solution in sight. The main cause of all these ills is the POVERTY. Float bonds which can be used by everybody rich or poor and are not debt to the state so there is no question of interest. How: Take the example of USA which is going through a great recession. USA borrows money by selling treasury bills and the interest based bonds. The suggestion is to sell these bonds on non interest basis EXAMPLE: ONE dollar buys 5 bonds on the condition that the amount should be $100000 or multiple of it. Fewer amounts will get the rate of four and three. This discount massive period is only for first month at the start of the implementation of this system. In the second month the rate will be 4 but the rate of 3 will apply to subsequent months for the same amount WHERE THESE BONDS WILL BE USED? 1. All state controlled services and commodities. EXAMPLE: A bill of (any service or Commodity)$100 can be paid with 200 bonds and there will be no exception to this rule .A NET DISCOUNT OF 60 %. A simple formula will apply: Total bill in dollars x2 is the number of bonds surrendered. Price in bonds will not be less than the cost price but without the direct indirect taxes and the duties which are added to the present to make it very expensive. It will attract at least 50 million people to take this opportunity as early as possible. And if one is sure of making 100% profit within 30 days there will be many more that will help themselves. RESULT - Government gets at least $15 trillion within a very short period of time of few days and much more in the rest of the year .THIS IS NOT A DEBT AS STATE HAS SOLD BONDS( Commodity) WHICH IS AN ALTERNATE CURRENCY AND DO NOT CARRY ANY INTEREST. One immediately thinks who will join this club bear the loss and this loss to the state will not be more than total year budget of$2.5 trillion which it collects in one year with all the taxes and the duties but the bond price is simply a cost price without any kind of tax or duty. So there is a net gain of approximately 2.5 trillion within a short period of time. WHO WILL SELL THESE BONDS? State will float tenders to will select a private agency (USMF) UNITED STATES MONITORY FUND JUST A NAME GIVEN TO THIS ORGANIZATION with the lowest bid WHERE AS second third and forth bidders will be auditors of USMF. This agency will employ at least 20 million unemployed on 10% commission basis and without any salary. These agents will have to pay $500 as an annual fee to USMF in order to build the infrastructure for the sale of bonds. Agents quota Will be$300000 per month or they will be allowed to sell their whole year quota in one day or in a month, This will only materialize if the agent shares his commission with the would be buyer. Greater the share of commission quicker the sale. This investor or a buyer will sell these bonds at the same rate of 5 per dollar and his bonds will sell like hot cakes every day as there is no condition of the amount of money to purchase of bonds. In this way even the poorest person will get the same rate or near the same rate as the investor except for the commission which he takes from the agent who makes almost 100% profit by only investing $100000 .He will sell these bonds repeatedly and will keep at least 6% profit every day till the demand lasts. NOW THINK HOW MUCH STATE HAS ACCUMULATED Much more than few years budget in matter of only one month.Economic

Association Mapping of Root Traits for Drought Tolerance in Bread Wheat

Bread wheat (Triticum aestivum L., 2n = 6x = 42, AABBDD) is one of the most important crops, making staple food for more than 40 countries and over 35% of the global population. Drought stress is among the major constraints to wheat production as it affects plant growth, gene expression and yield potential of the crop. Development of elite wheat cultivars with the ability to grow and reproduce in water-limited soils seems to be the most enduring solution of addressing drought stress. A total of 100 lines including well-adapted wheat cultivars were evaluated for important root traits and complemented with 102 PCR-based markers aiming to understand their genetic structure and to identify molecular markers that are closely associated to quantitative trait loci (QTLs) of important root traits. Alleles per locus are counted and polymorphic information content (PIC) values are calculated. Population structure of these lines was analyzed with general linear model (GLM) and mixed linear model (MLM) approaches for identification of QTLs associated with important root traits. The results indicated the presence of two novel QTLs on the homoeologous group 2 and group 5 of wheat that may be related to drought stress resistance. Our results may facilitate the development of agronomically desirable drought stress-resistant wheat germplasm

Effect of Different Moisture Stress Levels on Corn Growth in Field Lysimeters

Experiments were conducted in field lysimeters to investigate the effects of high water table positions (created by subirrigation practice) on com growth. Various plant growth parameters (plant dry matter, canopy height, and yield) were measured before, during, and after the excessively wet periods. Two regression models were developed to characterize corn yield production as a function of durations of excessively wet periods and water-table positions. Results indicated that subirrigation practices can improve com growing conditions. Less com yield reduction occurred when water tables were maintained at 15 cm than when water tables were maintained at the soil surface during the six-leaf stage

A comparative study of complications of vivax and falciparum malaria in Dehradun, India

Background: Traditionally Plasmodium falciparum has been considered to cause severe malaria while Plasmodium vivax is known to cause benign malaria. However many recent studies have shown that Plasmodium vivax is also responsible for many cases of severe malaria. There is scarcity of data on this topic from this region. The present study was conducted to find out clinical and pathological manifestations of vivax and falciparum malaria in Dehradun. Methods: The study period was of one and half years, from January 2012 to June 2013. Patients of 18 years of age or above it who were smear positive or antigen positive were included in the study.Results: one hundredand thirty nine patients were found to be suffering from malaria. 90 (64.7%) had vivax malaria, while 49 (35.3%) patients suffered from falciparum. The study of morbidity profile showed that the complications related to severity, earlier attributed to only falciparum is equally seen in vivax case. Low platelet count was the commonest finding in both groups. Other complications seen in both groups were those of severe anemia, cerebral malaria, ARDS, renal failure, hepatitis, leucocytopenia, pancytopenia, and shock. Mortality in the two groups was of the same order. Conclusions: Vivax malaria causes significant mortality and morbidity. The morbidity and patterns are almost similar in both vivax and falciparum malaria.

Exchange rate misalignment and economic growth: recent evidence in Malaysia

The present study aims at investigating the growth effects of real exchange rate misalignments in Malaysia over the period 1991:1-2009:4. The RER misalignment is built through the estimation of the NATREX equilibrium model. Using the Autoregressive Distributed Lag (ARDL) bounds testing approach to cointegration framework, the results indicate the presence of positive and significant relationship between the RER misalignment and economic growth. This finding obtained is consistent with the notion that the RER misalignment through the distortion in relative price has systematic influence on the pattern of economic development

A study of clinical and laboratory profile of dengue fever in a tertiary care centre of Uttarakhand, India

Background: Dengue is an important cause of mortality and morbidity in India. Many recent studies have shown varied clinical manifestations from different geographical locations. There is paucity of data on this topic from this region. The present study was conducted to find out the clinical features, complications, response to treatment and outcome of patients suffering from dengue in a tertiary care centre of Uttarakhand, India.Methods: The study was performed at SGRR Institute of Medical & Health Sciences, Dehradun, which is a tertiary care hospital of Uttrakhand. The study period was of 1 year from July 2012 to June 2013. Patients of 12 years of age or above it who were antigen positive or antibody positive were included in the study. All such patients who were admitted in the hospital underwent detailed clinical examination and investigation. Results: Dengue infection was identified in 140 patients. Thrombocytopenia was the commonest hematological abnormality. Splenomegaly, hepatomegaly, and hepatosplenomegaly, were common findings. Renal, hepatic and cerebral dysfunctions were noted. Mortality was seen in 5 (3.6%) patients. Encephalitis, shock and ARDS were associated with high mortality and poor outcome.Conclusions: Dengue is an important cause of mortality and morbidity in Uttarakhand. High index of suspicion, early diagnosis, monitoring of the clinical and laboratory parameters and prompt intervention may help in reducing the mortality.

A study of complications of scrub typhus in a tertiary health care institute of Uttarakhand, India

Background: Scrub typhus or tsutsugamushi disease is a febrile illness caused by Orientia tsutsugamushi. Uttarakhand State in the northern region of India has been witnessing increased incidence of this fever. There is paucity of data on this topic from this region. The present study was conducted to find out the clinical features, complications, response to treatment and outcome of patients suffering from scrub typhus in a tertiary health care institute of Uttarakhand, India.Methods: The study was performed at SGRR Institute of Medical & Health Sciences, Dehradun, which is a tertiary health care institute Uttrakhand. The study period was of 1year from December 2012 to November 2013. Patients of 12 years of age or above it who were IgM antibody positive by ELISA technique were included in the study. All such patients underwent detailed clinical examination and investigation. Results: 47 patients were found to be suffering from scrub typhus. The common symptoms noted fever, myalgias, headache, vomiting, diarrhoea, breathlessness, petechiae and jaundice. Common complications noticed were hepatitis (78.7%) acute respiratory distress syndrome (19.2%), thrombocytopenia (46.8%) and acute renal failure (31.9%), Mortality was seen in 3 (6.4%) patients.Conclusions: Scrub typhus is an important cause of mortality and morbidity in Uttarakhand. High index of suspicion, early diagnosis, monitoring of the clinical and laboratory parameters and prompt intervention may help in reducing the mortality.