Modelling of advanced submicron gate InGaAs/InAIAs pHEMTS and RTD devices for very high frequency applications

InP based InAlAs/InGaAs pseudomorphic High Electron Mobility Transistors (pHEMTs) have shown outstanding performances, which makes them prominent in high frequency mm-wave and submillimeter-wave applications. However, conventional InGaAs/InAlAs pHEMTs have major drawbacks, i.e., very low breakdown voltage and high gate leakage current. These disadvantages degrade device performance, especially in Monolithic Microwave Integrated Circuit (MMIC) low noise amplifiers (LNAs). The optimisation of InAlAs/InGaAs epilayer structures through advanced bandgap engineering together with gate length reduction from 1 m into deep sub-μm regime is the key solution to enabled high breakdown and ultra-high speed, low noise pHEMT devices to be fabricated. Concurrently, device modelling plays a vital role in the design and analysis of pHEMT device and circuit performance. Physical modeling becomes essential to fully characterise and understand the underlying physical phenomenon of the device, while empirical modelling is significant in circuit design and predicts device’s characteristic performance. In this research, the main objectives to accurately model the DC and RF characteristics of the two-dimensional (2D) physical modelling for sub-μm gate length for strained channel InAlAs/InGaAs/InP pHEMT has been accomplished and developed in ATLAS Silvaco. All modelled devices were optimised and validated by experimental devices which were fabricated at the University of Manchester; the sub-micrometer devices were developed with T-gate using I-line optical lithography. The underlying device physics insight are gained, i.e, the effects of changes to the device’s physical structure, theoretical concepts and its general operation, hence a reliable pHEMT model is obtained. The kink anomalies in I-V characteristics was reproduced and the 2D simulation results demonstrate an outstanding agreement with measured DC and RF characteristics. The aims to develop linear and nonlinear models for sub-μm transistors and their implementation in MMIC LNA design is achieved with the 0.25 m In0.7Ga0.3As/In0.52Al0.48As/InP pHEMT. An accurate technique for the extraction of empirical models for the fabricated active devices has been developed and optimised using Advance Design System (ADS) software which demonstrate excellent agreement between experimental and modelled DC and RF data. A precise models for MMIC passive devices have also been obtained and incorporated in the proposed design for a single and double stage MMIC LNAs in C- and X-band frequency. The single stage LNA is designed to achieve maximum gain ranging from 9 to 13 dB over the band of operation while the gain is increased between 20 dB and 26 dB for the double stage LNA designs. A noise figure of less than 1.2 dB and 2 dB is expected respectively, for the C- and X-band LNA designed while retaining stability across the entire frequency bands. Although the RF performance of pHEMT is being vigorously pushed towards terahertz region, novel devices such as Resonant Tunnelling Diode (RTD) are needed to support future ultra-high speed, high frequency applications especially when it comes to THz frequencies. Hence, the study of physical modelling is extended to quantum modelling of an advanced In0.8Ga0.2As/AlAs RTD device to effectively model both large size and submicron RTD using Silvaco’s ATLAS software to reproduce the peak current density, peak-to-valley-current ratio (PVCR), and negative differential resistance (NDR) voltage range. The simple one-dimensional physical modelling for the RTD devices is optimised to achieve an excellent match with the fabricated RTD devices with variations in the spacer thickness, barrier thickness, quantum well thickness and doping concentration

The Evaluation of Route Guidance Systems

BACKGROUND We were commissioned by the Transport and Road Research Laboratory to: "collaborate with the German government and their representatives who are responsible for conducting the LISB trial in Berlin in order to produce an agreed methodology, which is acceptable in both Germany and the UK, for assessing the automatic route guidance systems which will be provided in Berlin and London." The brief suggested a number of aspects to be included, and required detailed proposals, timescales and costs for implementation in London. 1.1.2 The background to the brief lies in decisions to introduce pilot automatic route guidance systems in the two cities. The principles of the systems are similar, and have been described in detail elsewhere (Jeffery, 1987). In brief, they involve : (i) a central computer which retains information on a specified road network, which is updated using real time information from the equipment users; (ii) infra red beacons at selected junctions which transmit information to equipped vehicles and receive information from those vehicles; (iii) in-vehicle equipment which includes a dead-reckoning system for position finding, a device for requesting guidance and specifying the destination, a micro-computer which selects the optimal route, and a display which indicates when a turn is required on the main network, and the compass direction and distance to the final destination; iv) transmission from the equipped vehicles of origin, requested destination, links used since passing the last beacon and, for each link, the time of entry and departure and time spent delayed. It is this travel time information which is used to update the central computer's knowledge of the best routes. (Continues..

Tradeoffs among Free-flow Speed, Capacity, Cost, and Environmental Footprint in Highway Design

This paper investigates differentiated design standards as a source of capacity additions that are more affordable and have smaller aesthetic and environmental impacts than expressways. We consider several tradeoffs, including narrow versus wide lanes and shoulders on an expressway of a given total width, and high-speed expressway versus lower-speed arterial. We quantify the situations in which off-peak traffic is sufficiently great to make it worthwhile to spend more on construction, or to give up some capacity, in order to provide very high off-peak speeds even if peak speeds are limited by congestion. We also consider the implications of differing accident rates. The results support expanding the range of highway designs that are considered when adding capacity to ameliorate urban road congestion.Highway design; Capacity; Free-flow speed; Parkway

Income, Income Inequality and the “Hidden Epidemic” of Traffic Fatalities

Few, if any, epidemics responsible for 20 million severe injuries and/or deaths each year, globally, receive less public attention than do traffic accidents truly making them a “hidden epidemic”. Worse yet, the epidemic is growing as evidenced by World Health Organization data which show deaths from traffic accidents increasing by 20 percent between 1990 and 2002. In this paper we examine how a country’s stage of development and its distribution of income affect its traffic fatality rate. In our theoretical analysis, we show that traffic fatalities should have a nonlinear relationship with a country’s level of per capita income while being a decreasing function of income equality. We test our model’s predictions by evaluating data from 79 countries between 1970 and 2000, taking into account other factors that influence traffic fatalities like the motorization rate, health care networks, education, and alcohol consumption and find strong evidence of the theoretical model’s predictions. Specifically, the empirical results indicate that traffic fatalities are negatively related to income equality throughout its range and also are negatively related to per capita income, above a threshold of about $11,500.Vulnerable road users, traffic safety interventions, per capita income, income inequality

Promoting Bicycle Commuter Safety, Research Report 11-08

We present an overview of the risks associated with cycling to emphasize the need for safety. We focus on the application of frameworks from social psychology to education, one of the 5 Es—engineering, education, enforcement, encouragement, and evaluation. We use the structure of the 5 Es to organize information with particular attention to engineering and education in the literature review. Engineering is essential because the infrastructure is vital to protecting cyclists. Education is emphasized since the central focus of the report is safety

Accident Analysis and Prevention: Course Notes 1987/88

This report consists of the notes from a series of lectures given by the authors for a course entitled Accident Analysis and Prevention. The course took place during the second term of a one year Masters degree course in Transport Planning and Engineering run by the Institute for Transport Studies and the Department of Civil Engineering at the University of Leeds. The course consisted of 18 lectures of which 16 are reported on in this document (the remaining two, on Human Factors, are not reported on in this document as no notes were provided). Each lecture represents one chapter of this document, except in two instances where two lectures are covered in one chapter (Chapters 10 and 14). The course first took place in 1988, and at the date of publication has been run for a second time. This report contains the notes for the initial version of the course. A number of changes were made in the content and emphasis of the course during its second run, mainly due to a change of personnel, with different ideas and experiences in the field of accident analysis and prevention. It is likely that each time the course is run, there will be significant changes, but that the notes provided in this document can be considered to contain a number of the core elements of any future version of the course

Child pedestrian safety en route to and from rural schools: A case study

This research examines the safety hazards faced by child pedestrians at rural schools within the Waipa District. The main objectives of this research were to identify hazards child pedestrians face, to identify current counter-measures to these hazards, and to evaluate the regulations and policies pertaining to these counter-measures and child pedestrian safety. Meeting these objectives then allowed the design of possible counter-measures to the hazards faced by rural child pedestrians. The ultimate goal of this research was to improve child pedestrian safety at rural schools

Preventing child pedestrian injuries and deaths arising from vehicle-child accidents in domestic driveways: An action research project

This research was a three-fold investigation into the viability of previous recommendations for vehicle-related child driveway accident safety . Firstly, the groups most at risk of these types of accidents were determined in order that they could be specifically considered when reviewing the practicalities of previous recommendations . Secondly, the feasibility of previous recommendations was systematically examined through both an extensive literature review and key and expert informant interviews . Based on these, the likelihood of implementation of previous safety recommendations for the identified high risk groups was ascertained, providing a basis on which to abandon some previous recommendations, remove obstacles to others which would enhance practicability and generate further recommendations that would be tenable for the at-risk groups in particular. The key findings of this research were, foremost, that there is a noticeable lack of specific reference to vehicle-related child driveway accidents in any legislation or safety guidelines, as well as a shortage of official data that deal expressly with this type of accident. Further, it was found that the major obstacles to the implementation of previous recommendations - particularly the environmental ones - were cost, autonomy, and spatial constraints. While several recommendations were abandoned due to factors such as unproven or dubious effectiveness and/or prohibitive cost, it was found that the most viable recommendations were characterised by their relatively low cost for the families involved. These recommendations were typically environmental or educational in nature. Thus, the recommendations in this report include some moderate regulatory changes to facilitate greater uptake of environmental and behaviour-modifying recommendations as well as practical ideas that all need to be part of a cohesive campaign to address the issue of vehicle-related child driveway accidents in New Zealand