Semiconductor Electronics: Materials, Devices and Simple Circuits semiconductors. However, after 1990, a few semiconductor devices using organic semiconductors and semiconducting polymers have been developed signalling the birth of a futuristic technology of polymer-electronics and molecular-electronics. In this chapter, we will restrict. Describe how current is produced in a semiconductor Describe the properties of n-type and p-type semiconductors Describe how a pn junction is formed Atom Proton Electron Shell Valence Ionization Free electron Orbital Insulator Conductor Semiconductor Silicon Crystal.

Final Project Assignment

The end-of-the-term assignment in 6.772/SMA5111 is to write an 8-10 page paper and to prepare a 10-15 minute class presentation on a topic of current interest in the academic and industrial research communities that involves compound semiconductors and the devices and concepts discussed in class. Your topic can relate to your own research but if it does it should be peripheral to your primary thesis thrust and deal with some aspect you would not otherwise explore in depth. It might, for example, deal with an alternative approach you are not pursuing.

The first part of the assignment is to submit in Recitation 9 (1) a preliminary title, (2) a draft outline, and (3) an initial set of references for your end-of-the-term assignment. The idea of this exercise is to get you started. It will also help me schedule the presentations at the end of the term. It is alright if what you submit for your end-ofthe-term assignment looks different when finished from what you submit in Recitation 9 (Lecture 21).

Your paper and presentation should provide the readers with a good intuitive understanding of the topic and provide them with the information they need to assess developments in the field and put them in context amongst the various alternatives. Indicate what problem is being solved, how it is being addressed, and whether the approach has merit.

Several students have asked for more guidance on the paper. Here is some:

General Comments (in addition to the original announcement)

Your paper can take many forms, but two of the most common are the following:

1. Critique of a Specific Paper: Find an article that looks interesting to you and that describes a particular approach to solving a problem, and review that paper, giving background on the problem and issues involved with it, including what the state of the field was prior to this paper, and then describe and evaluate the contribution of the paper. Simply put, say what they claim to have done, explain why anyone should care, and argue whether or not you think they have made a significant contribution and really solved a problem.
2. Review of the Present Status of a Given Area: Find a recent review article and a couple of more new research articles on the same topic. Present an overview of the area outlining the goal and the reason it is of interest, what the challenges are in reaching the goal, which challenges have been solved and where challenges remain and/or where the present solutions need further improvement.

Examples of Past Project/Presentation Titles

Mode Control in VCSELs
Quantum Cascade Lasers
Sunlight-blind UV Detectors
GaN Power Devices
Analysis of an MSM Photodetector
GaN Blue Laser Diodes
Antimonides and their Application to Optical Devices
1.55 µm Vertical Cavity Surface Emitting Lasers
SiGe HBT Technology for RF Applications
Light Confinement and Guiding in Photonic Crystals
Monolithic Integration of GaAs and Si Devices

Suggestions on Where to Look for Ideas

The tables of contents of the following letters journals are a good place to get an idea of what topics people are working on. When you find something that interests you, start a more intensive search using the background references in the article you find and on the web.

Applied Physics Letters
IEEE Photonics Technology Letters
Electronics Letters
IEEE Electron Device Letters

Sample Student Presentations

Note: Some of the illustrative figures within these presentations are absent due to copyright restrictions.

Semiconductor Pdf Download

Conducting Polymeric Materials as they Pertain to Supercapacitors, by David A. New (PDF)

Compound Semiconductor Based Micro-Thermophotovoltaic Power Generation Technologies, by Francis M. O'Sullivan (PDF) Courtesy of Francis O'Sullivan.

Auger Recombination in A^IIIB^V Compound Semiconductors: Non-radiative Losses in Quantum Wells and Superlattices, by Georgii Samsonidze (PDF) Courtesy of Georgii Samsonidze.

Recent Developments in HEMT Cryogenic Low-noise Amplifiers, by Janice C. Lee (PDF) Courtesy of Janice Lee.

Energy Flow in Semiconductor Devices and its Applications for Semiconductor Laser Diodes, by Ronggui Yang (PDF) Courtesy of Ronggui Yang.

The Use of Strain in Silicon Germanium Heterostructure MOSFET Technology, by Stuart Laval (PDF) Courtesy of Stuart Laval.

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Project On Semiconductor Pdf Format

Semiconductor, any of a class of crystalline solids intermediate in electrical conductivity between a conductor and an insulator. Semiconductors are employed in the manufacture of various kinds of electronic devices, including diodes, transistors, and integrated circuits. Such devices have found wide application because of their compactness, reliability, power efficiency, and low cost. As discrete components, they have found use in power devices, optical sensors, and light emitters, including solid-state lasers. They have a wide range of current- and voltage-handling capabilities and, more important, lend themselves to integration into complex but readily manufacturable microelectronic circuits. They are, and will be in the foreseeable future, the key elements for the majority of electronic systems, serving communications, signal processing, computing, and control applications in both the consumer and industrial markets.

Semiconductor materials

Solid-state materials are commonly grouped into three classes: insulators, semiconductors, and conductors. (At low temperatures some conductors, semiconductors, and insulators may become superconductors.) The figure shows the conductivities σ (and the corresponding resistivities ρ = 1/σ) that are associated with some important materials in each of the three classes. Insulators, such as fused quartz and glass, have very low conductivities, on the order of 10⁻¹⁸ to 10⁻¹⁰siemens per centimetre; and conductors, such as aluminum, have high conductivities, typically from 10⁴ to 10⁶ siemens per centimetre. The conductivities of semiconductors are between these extremes and are generally sensitive to temperature, illumination, magnetic fields, and minute amounts of impurity atoms. For example, the addition of about 10 atoms of boron (known as a dopant) per million atoms of silicon can increase its electrical conductivity a thousandfold (partially accounting for the wide variability shown in the preceding figure).

The study of semiconductor materials began in the early 19th century. The elemental semiconductors are those composed of single species of atoms, such as silicon (Si), germanium (Ge), and tin (Sn) in column IV and selenium (Se) and tellurium (Te) in column VI of the periodic table. There are, however, numerous compound semiconductors, which are composed of two or more elements. Gallium arsenide (GaAs), for example, is a binary III-V compound, which is a combination of gallium (Ga) from column III and arsenic (As) from column V. Ternary compounds can be formed by elements from three different columns—for instance, mercury indium telluride (HgIn₂Te₄), a II-III-VI compound. They also can be formed by elements from two columns, such as aluminum gallium arsenide (Al_xGa_{1 − x}As), which is a ternary III-V compound, where both Al and Ga are from column III and the subscript x is related to the composition of the two elements from 100 percent Al (x = 1) to 100 percent Ga (x = 0). Pure silicon is the most important material for integrated circuit applications, and III-V binary and ternary compounds are most significant for light emission.

Prior to the invention of the bipolar transistor in 1947, semiconductors were used only as two-terminal devices, such as rectifiers and photodiodes. During the early 1950s germanium was the major semiconductor material. However, it proved unsuitable for many applications, because devices made of the material exhibited high leakage currents at only moderately elevated temperatures. Since the early 1960s silicon has become by far the most widely used semiconductor, virtually supplanting germanium as a material for device fabrication. The main reasons for this are twofold: (1) silicon devices exhibit much lower leakage currents, and (2) silicon dioxide (SiO₂), which is a high-quality insulator, is easy to incorporate as part of a silicon-based device. Thus, silicon technology has become very advanced and pervasive, with silicon devices constituting more than 95 percent of all semiconductor products sold worldwide.

Many of the compound semiconductors have some specific electrical and optical properties that are superior to their counterparts in silicon. These semiconductors, especially gallium arsenide, are used mainly for optoelectronic and certain radio frequency (RF) applications.

Electronic properties

The semiconductor materials described here are single crystals; i.e., the atoms are arranged in a three-dimensional periodic fashion. Part A of the figure shows a simplified two-dimensional representation of an intrinsic (pure) silicon crystal that contains negligible impurities. Each silicon atom in the crystal is surrounded by four of its nearest neighbours. Each atom has four electrons in its outer orbit and shares these electrons with its four neighbours. Each shared electron pair constitutes a covalent bond. The force of attraction between the electrons and both nuclei holds the two atoms together. For isolated atoms (e.g., in a gas rather than a crystal), the electrons can have only discrete energy levels. However, when a large number of atoms are brought together to form a crystal, the interaction between the atoms causes the discrete energy levels to spread out into energy bands. When there is no thermal vibration (i.e., at low temperature), the electrons in an insulator or semiconductor crystal will completely fill a number of energy bands, leaving the rest of the energy bands empty. The highest filled band is called the valence band. The next band is the conduction band, which is separated from the valence band by an energy gap (much larger gaps in crystalline insulators than in semiconductors). This energy gap, also called a bandgap, is a region that designates energies that the electrons in the crystal cannot possess. Most of the important semiconductors have bandgaps in the range 0.25 to 2.5 electron volts (eV). The bandgap of silicon, for example, is 1.12 eV, and that of gallium arsenide is 1.42 eV. In contrast, the bandgap of diamond, a good crystalline insulator, is 5.5 eV.

At low temperatures the electrons in a semiconductor are bound in their respective bands in the crystal; consequently, they are not available for electrical conduction. At higher temperatures thermal vibration may break some of the covalent bonds to yield free electrons that can participate in current conduction. Once an electron moves away from a covalent bond, there is an electron vacancy associated with that bond. This vacancy may be filled by a neighbouring electron, which results in a shift of the vacancy location from one crystal site to another. This vacancy may be regarded as a fictitious particle, dubbed a “hole,” that carries a positive charge and moves in a direction opposite to that of an electron. When an electric field is applied to the semiconductor, both the free electrons (now residing in the conduction band) and the holes (left behind in the valence band) move through the crystal, producing an electric current. The electrical conductivity of a material depends on the number of free electrons and holes (charge carriers) per unit volume and on the rate at which these carriers move under the influence of an electric field. In an intrinsic semiconductor there exists an equal number of free electrons and holes. The electrons and holes, however, have different mobilities; that is, they move with different velocities in an electric field. For example, for intrinsic silicon at room temperature, the electron mobility is 1,500 square centimetres per volt-second (cm²/V·s)—i.e., an electron will move at a velocity of 1,500 centimetres per second under an electric field of one volt per centimetre—while the hole mobility is 500 cm²/V·s. The electron and hole mobilities in a particular semiconductor generally decrease with increasing temperature.

Electrical conduction in intrinsic semiconductors is quite poor at room temperature. To produce higher conduction, one can intentionally introduce impurities (typically to a concentration of one part per million host atoms). This is called doping, a process that increases conductivity despite some loss of mobility. For example, if a silicon atom is replaced by an atom with five outer electrons, such as arsenic (see part B of the figure), four of the electrons form covalent bonds with the four neighbouring silicon atoms. The fifth electron becomes a conduction electron that is donated to the conduction band. The silicon becomes an n-type semiconductor because of the addition of the electron. The arsenic atom is the donor. Similarly, part C of the figure shows that, if an atom with three outer electrons, such as boron, is substituted for a silicon atom, an additional electron is accepted to form four covalent bonds around the boron atom, and a positively charged hole is created in the valence band. This creates a p-type semiconductor, with the boron constituting an acceptor.

Semiconductor Market Pdf