Write a 5-8 page report and develop a 5 to 6 minute presentation (under 4: 30 or

Question

Write a 5-8 page report and develop a 5 to 6 minute presentation (under 4: 30 or over 6: 30) minutes you will lose points) to be given in class on a topic related to semiconductor physics. Generally, the topic should be outside of what is covered in class or in the book. If your topic is covered in the book, but not in class, you MAY use it, BUT you still must have at least one additional peer-reviewed journal article to support your topic. List of suggested topics: --- detail a ternary semiconductor, its properties, applications, why or why not it's in/not in widespread use --- detail applications and characteristics of any semiconductor that is not covered in the book (Si, GaAs, Ge) --- detail the semiconductor laser, especially the YELLOW or blue laser (have not seen a report on a yellow laser) --- detail the development of the blue LED, its characteristics and promising applications --- high power semiconductor devices - focus on the physics and characteristics --- superconductivity-only specific semiconductor-related applications, not just superconductivity in general --- copper chip manufacturing technology --- MEMs --- other related topics The written paper should be professionally done. A cover page with name, class, title, etc. It should be well-written and spell-checked and proof read. (Swapping with another group for review is be a great ideal) I will not count off for minor errors, but if it is heavily doped with errors, you will lose points. There should be a reference page that details all of your sources. The book may be used, but you should have at least 3 other sources, and at least journal articles. Single spacing is fine, but please use a 10 to 12 point font. Figures should be labeled and when specific information is used, references should be directly cited. If you number them, you can site them with a simple [#]. To avoid the spacing/font/illustration tricks in order to complete some arbitrary page count, I do not have one. I am expecting enough technical detail to convince me you learned about your topic. Get into the physics of it but do not block copy a bunch of equation derivations (YOU falling asleep while you are talking OR ME falling asleep while reading does not bode well for your grade). Use the results and discuss why they are relevant or how they are used from a practical standpoint. Feel free to include some applications, but the main focus should be on the practical use and the conceptual theory. As far as the content, the grade will be based upon how well you communicate your comprehension and knowledge of the topic.

Explanation / Answer

Semiconductor: A semiconductor is a material that has a resistivity value in between that of a conductor and an insulator. The conductivity of a semiconductor material can be varied under an external electric field.

Ternary semiconductor:

1) Ternary semiconductors, which consist of various elements, have widely ranging Physical properties.
2) They have therefore many possible applications.
3) The physical Properties which may vary, include band gaps, crystal lattice structures, electron and Hole mobilities, optical properties, thermal conductivity, and so on.
4) By selecting appropriate Ternary semiconductor materials, it becomes possible to realize various devices, which cannot be achieved using the main elemental semiconductor material, silicon.
5) Among many Ternary Semiconductor Compounds, which consist of more than two elements, only some show semiconductor properties.
6) Ternary Semiconductor Compounds, which show semiconductor properties, have the following features
(i) The conductivity of the Ternary semiconductor is electronic. Ionic conductivity is excluded.
(ii) Ternary Conductivity is largely increased as a function of temperature.
(iii) Ternary Conductivity is very dependent on the kind of impurities and their concentrations

7) Ternary Semiconductor Compound also have tetrahedral bonds but
they include not only covalent bonds but also ionic bonds. This is because compounds are formed from different elements, which have different electro negativity.
8) Electo negativity indicates the strength with which atoms attract electrons. The difference of electro negativity of constituent elements is therefore an indication of the ionicity strength.
9)Ternary compound semiconductors Materials that show semi conducting properties have to obey the following laws.
(i) In the case of elemental semiconductors, the constituent atom has eight electrons including electrons, which form covalent bonds, and these electrons produce s , p orbital closed shells.
(ii) For compound semiconductors, the condition (i) is applied to each constituent atom.
Elements from IV group to VII group satisfy the first condition (i) and following the second condition
(ii) compound semiconductors include these elements. This is repre-
sented by the following equation.
ne/na+ b =8
Here: ne is the number of valence electrons per molecule
and na is the number of group IV to VII atoms per molecule.
b is the average number of covalent bonds formed by one of these atoms with other atoms of groups IV to VII.

BAND STRUCTURES, BANDGAPS AND LATTICE CONSTANTS
1) When atoms are close enough to form crystals, electron orbital overlap and each electron has different energy levels due to the Pauli law.
2) These band structures can be obtained by solving the Schrodinger equation under periodic potentials due to crystal periodicity.
3) There are various approaches to solving the Schrodinger equation such as linear combination of atomic orbital, tight binding approximation, pseudopotential method, and k . p perturbation method and the orthogonalized plane wave method.
4)To show electron energies, it is sufficient to represent the energy as a function of wave number k.
Band Gaps: In Ternary semiconductors, electrons are forbidden to have a certain range of energies and they are called band gaps.
5) Ternary semiconductors are categorized to two types as
direct and indirect transition materials.
6) Direct Transition: electrons can be excited from the valence band to the conduction band without any phonon generation.
7) In indirect transition: electrons are recombined via holes with phonon interactions.
8) Lattice constant: The lattice constant in Ternary Semiconductors is systematically changed. It becomes smaller when the compounds consist of smaller diameter atoms, and becomes larger when the compounds
consist of larger diameter atoms.
9) Relation of M.W, M.P, and L.C: When the molecular weight becomes larger, the melting point becomes lower. This is because when the molecular weight becomes larger, the lattice constant becomes larger and the binding force becomes smaller. Even for similar molecular weights, the melting point becomes higher with the progression
of 11-VI compound > 111-VI compound > Si, Ge. This is because the binding force becomes larger when the ionicity becomes large.

ELECTRICAL PROPERTIES OF TERNARY SEMICONDUCTORS:
Carrier Concentration
Carrier concentrations in Ternary semiconductors are determined as a thermal equilibrium between thermal excitation of electrons and ionization of impurities and ionization of defect levels.
(1) Intrinsic semiconductors
Electron concentration and hole concentration in Ternary semiconductors can be represented according to the Boltzman statistics.
Here, Eg= Eke – EV is the energy band gap.
In the case of intrinsic materials where impurities are negligible, n=p
(2) Donors and acceptors:
In reality, in Ternary semiconductor materials, there are always some impurities and defects and some of them are ionized and affect carrier concentrations.
Impurities, which have more valence electrons than substituted host constituent atoms and can be thermally ionized act as donors. They offer electrons in the conduction band.
Impurities, which have fewer valence electrons than substituted host constituent atoms and can be thermally ionized act as acceptors. They attract electrons thus leaving holes in the valence band.

(3) Fermi level:
Fermi Energy level: The position of the Fermi level is important to characterize the electrical properties of Ternary compound semiconductors.
The Fermi level is determined as a function of the concentrations of various defects such as donors, acceptors and deep levels.

Application of ternary semiconductor:

1) photodetector applications

CHARACTERISTICS OF SILICON SEMICONDUCTOR

1.PHYSICAL

Silicon is a solid at room temperature, with a melting point of 1,414 °C (2,577 °F) and a boiling point of 3,265 °C (5,909 °F). Like water, it has a greater density in a liquid state than in a solid state and it expands when it freezes, unlike most other substances. With a relatively high thermal conductivity of 149 W·m1·K1, silicon conducts heat well.

In its crystalline form, pure silicon has a gray color and a metallic luster. Like germanium, silicon is rather strong, very brittle, and prone to chipping. Silicon, like carbon and germanium, crystallizes in a diamond cubic crystal structure with a lattice spacing of 0.5430710 nm (5.430710 Å).

The outer electron orbital of silicon, like that of carbon, has four valence electrons. The 1s, 2s, 2pand 3s subshells are completely filled while the 3p subshell contains two electrons out of a possible six.

Silicon is a semiconductor. It has a negative temperature coefficient of resistance, since the number of free charge carriers increases with temperature. The electrical resistance of single crystal silicon significantly changes under the application of mechanical stress due to the piezoresistive effect. Heavily boron-doped silicon is a type II superconductor with a transition temperature Tc of 0.4 K.

2.CHEMICAL

Silicon is a metalloid, readily donating or sharing its four outer electrons, and it typically forms four bonds. Like carbon, its four bonding electrons enable it to combine with many other elements or compounds to form a wide range of compounds. Unlike carbon, it can accept additional electrons and form five or six bonds in a sometimes more labile silicate form. Tetra-valent silicon is relatively inert; it reacts with halogens and dilute alkalis, but most acids (except some hyper-reactive combinations of nitric acid and hydrofluoric acid) have no effect on it.

APPLICATIONS OF SILICON SEMICONDUCTOR

Most elemental silicon produced remains as a ferrosilicon alloy, and only about 20% is refined to metallurgical grade purity (a total of 1.3–1.5 million metric tons/year). An estimated 15% of the world production of metallurgical grade silicon is further refined to semiconductor purity.However, the economic importance of this small very high-purity fraction (especially the ~ 5% which is processed to monocrystalline silicon for integrated circuits) is disproportionately large.

Pure monocrystalline silicon is used to produce silicon wafers used in the semiconductor industry, in electronics, and in some high-cost and high-efficiency photovoltaic applications. Pure silicon is an intrinsic semiconductor, which means that unlike metals, it conducts electron holesand electrons released from atoms by heat; silicon's electrical conductivity increases with higher temperatures. Pure silicon has too low a conductivity (i.e., too high a resistivity) to be used as a circuit element in electronics. In practice, pure silicon is doped with small concentrations of certain other elements, which greatly increase its conductivity and adjust its electrical response by controlling the number and charge (positive or negative) of activated carriers. Such control is necessary for transistors, solar cells, semiconductor detectors, and other semiconductor devices used in the computer industry and other technical applications. In silicon photonics, silicon can be used as a continuous wave Raman laser medium to produce coherent light, though it is ineffective as an everyday light source.

In common integrated circuits, a wafer of monocrystalline silicon serves as a mechanical support for the circuits, which are created by doping and insulated from each other by thin layers of silicon oxide, an insulator that is easily produced by exposing the element to oxygen under the proper conditions. Silicon has become the most popular material for both high power semiconductors and integrated circuits because it can withstand the highest temperatures and greatest electrical activity without suffering avalanche breakdown (an electron avalanche is created when heat produces free electrons and holes, which in turn pass more current, which produces more heat). In addition, the insulating oxide of silicon is not soluble in water, which gives it an advantage over germanium (an element with similar properties which can also be used in semiconductor devices) in certain fabrication techniques.

Monocrystalline silicon is expensive to produce, and is usually justified only in production of integrated circuits, where tiny crystal imperfections can interfere with tiny circuit paths. For other uses, other types of pure silicon may be employed. These include hydrogenated amorphous silicon and upgraded metallurgical-grade silicon (UMG-Si) used in the production of low-cost, large-area electronics in applications such as liquid crystal displays and of large-area, low-cost, thin-film solar cells. Such semiconductor grades of silicon are either slightly less pure or polycrystalline rather than monocrystalline, and are produced in comparable quatities as the monocrystalline silicon: 75,000 to 150,000 metric tons per year. The market for the lesser grade is growing more quickly than for monocrystalline silicon. By 2013, polycrystalline silicon production, used mostly in solar cells, was projected to reach 200,000 metric tons per year, while monocrystalline semiconductor grade silicon was expected to remain less than 50,000 tons/year.

YELLOW LASER

TTL modulation, analog modulation and fiber coupling options available in it

DEVELOPMENT OF BLUE LED

Three scientists have jointly earned the Nobel Prize in physics for their work on blue LEDs, or light-emitting diodes. Why blue in particular? Well, blue was the last and most difficult ,advance required to create white LED light. And with white LED light, companies are able to create smartphone and computer screens, as well as light bulbs that last longer and use less electricity than any bulb invented before.

LEDs are basically semiconductors that have been built so they emit light when they're activated. Different chemicals give different LEDs their colors. Engineers made the first LEDs in the 1950s and 60s. Early iterations included laser-emitting devices that worked only when bathed in liquid nitrogen. At the time, scientists developed LEDs that emitted everything from infrared light to green light… but they couldn't quite get to blue. That required chemicals, including carefully-created crystals, that they weren't yet able to make in the lab.Once they did figure it out, however, the results were remarkable. A modern white LED lightblub converts more than 50 percent of the electricity it uses into light. Compare that to the 4 percent conversion rate for incandescent bulbs, and you have one efficient bulb. Besides saving money and electricity for all users, white LED'S efficiency makes them appealing for getting lighting to folks living in regions without electricity supply. A solar installation can charge an LED lamp to last a long time, allowing kids to do homework at night and small businesses to continue working after dark.

CHARACTERISTICS OF BLUE LED

wavelength 460-490 nm

typical efficacy 37 LM/W

typical efficacy 0.35 W/W

voltage drop 2.5 - 3.5 v

semiconductor material used :

zinc selenide, indium gallium nitride,silicon carbide, silicon.

APPLICATION

HIGH POWER SEMICONDUCTOR DEVICES

A power semiconductor device is a semiconductor device used as a switch or rectifier in power electronics; a switch-mode power supply is an example. Such a device is also called a power device or, when used in an integrated circuit, a power IC.

A power semiconductor device is usually used in "commutation mode" (i.e., it is either on or off), and therefore has a design optimized for such usage; it should usually not be used in linear operation. Linear power circuits are widespread as voltage regulators, audio amplifiers, and radio frequency amplifiers.

Power semiconductors are found in systems delivering as little as a few tens of milliwatts for a headphone amplifier, up to around a gigwatt in a high voltage direct currenttransmission line.

DEVICES:

diode: Uni-polar, uncontrolled, switching device used in applications such as rectification and circuit directional current control. Reverse voltage blocking device, commonly modeled as a switch in series with a voltage source, usually 0.7 VDC. The model can be enhanced to include a junction resistance, in order to accurately predict the diode voltage drop across the diode with respect to current flow.

SCR:This semi-controlled device turns on when a gate pulse is present and the anode is positive compared to the cathode. When a gate pulse is present, the device operates like a standard diode. When the anode is negative compared to the cathode, the device turns off and blocks positive or negative voltages present. The gate voltage does not allow the device to turn off.

thyristor:The thyristor is a family of three-terminal devices that include SCRs, GTOs, and MCT. For most of the devices, a gate pulse turns the device on. The device turns off when the anode voltage falls below a value (relative to the cathode) determined by the device characteristics. When off, it is considered a reverse voltage blocking device.

GTO:The gate turn-off thyristor, unlike an SCR, can be turned on and off with a gate pulse. One issue with the device is that turn off gate voltages are usually larger and require more current than turn on levels. This turn off voltage is a negative voltage from gate to source, usually it only needs to be present for a short time, but the magnitude s on the order of 1/3 of the anode current. A snubber circuit is required in order to provide a usable switching curve for this device. Without the snubber circuit, the GTO cannot be used for turning inductive loads off. These devices, because of developments in IGCT technology are not very popular in the power electronics realm. They are considered controlled, uni-polar and bi-polar voltage blocking

TRIAC:The triac is a device that is essentially an integrated pair of phase-controlled thyristors connected in inverse-parallel on the same chip.[8] Like an SCR, when a voltage pulse is present on the gate terminal, the device turns on. The main difference between an SCR and a Triac is that both the positive and negative cycle can be turned on independently of each other, using a positive or negative gate pulse. Similar to an SCR, once the device is turned on, the device cannot be turned off. This device is considered bipolar and reverse voltage blocking.

BJT:The BJT cannot be used at high power; they are slower and have more resistive losses when compared to MOSFET type devices. To carry high current, BJTs must have relatively large base currents, thus these devices have high power losses when compared to MOSFET devices. BJTs along with MOSFETs, are also considered unipolar and do not block reverse voltage very well, unless installed in pairs with protection diodes. Generally, BJTs are not utilized in power electronics switching circuits because of the I2R losses associated with on resistance and base current requirements.[6]BJTs have lower current gains in high power packages, thus requiring them to be set up in Darlington configurations in order to handle the currents required by power electronic circuits. Because of these multiple transistor configurations, switching times are in the hundreds of nanoseconds to microseconds. Devices have voltage ratings which max out around 1500 V and fairly high current ratings. They can also be paralleled in order to increase power handling, but must be limited to around 5 devices for current sharing.

IGBT:These devices have the best characteristics of MOSFETs and BJTs. Like MOSFET devices, the insulated gate bipolar transistor has a high gate impedance, thus low gate current requirements. Like BJTs, this device has low on state voltage drop, thus low power loss across the switch in operating mode. Similar to the GTO, the IGBT can be used to block both positive and negative voltages. Operating currents are fairly high, in excess of 1500 A and switching voltage up to 3000 V.[7] The IGBT has reduced input capacitance compared to MOSFET devices which improves the Miller feedback effect during high dv/dt turn on and turn off.

MCT, IGCT , POWER MOSFET etc.

SUPERCONDUCTIVTY

Since the discovery of superconductivity in diamond, much attention has been given to the issue of superconductivity in semiconductors. Because diamond has a large band gap of 5.5 eV, it is called a wide-gap semiconductor. Upon heavy boron doping over 3×1020 cm3, diamond becomes metallic and demonstrates superconductivity at temperatures below 11.4 K. This discovery implies that a semiconductor can become a superconductor upon carrier doping. Recently, superconductivity was also discovered in boron-doped silicon and SiC semiconductors. The number of superconducting semiconductors has increased. In 2008 an Fe-based superconductor was discovered in a research project on carrier doping in a LaCuSeO wide-gap semiconductor. This discovery enhanced research activities in the field of superconductivity, where many scientists place particular importance on superconductivity in semiconductors.

COPPER CHIP MANUFACTURING TECHNOLOGY

The first silicon integrated circuit technology that incorporates copper on-chip wiring. This technology, which combines industry-leading CMOS ULSI devices with 6 levels of hierarchically-scaled Cu metallization, has reached the point of manufacturing, after passing the qualification tests required to prove feasibility, yield, reliability, and manufacturability. The discussion of the change from Al to Cu interconnects for ULSI encompasses a wide variety of issues. This paper attempts to address these by way of example, from the broad range of detailed studies that have been performed in the course of developing these so-called 'copper chips'. Motivational issues are covered by comparative modeling of performance aspects and cost. The technology parameters and features are shown, as well as data relating to the process integration, electrical yield and parametric behavior, early manufacturing data, high-frequency modeling and measurements, noise and clock skew. The viability of this technology is indicated by results from reliability stressing, as well as the first successful demonstrations of fully functional SRAM, DRAM, and microprocessor chips with Cu wiring. The advantages of integrated Cu wiring may be applied even more broadly in the future. An example shown here is the achievement of very high-quality integrated inductors; these may help prospects for complete integration of RF and wireless communications chips onto silicon.

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