Required Textbook: M.S. Tyagi, "Introduction to Semiconductor Materials and Devices," Wiley, New York (1991).
Instructor: Ali
Serpengüzel
Office: A-277
Ext: 312
e-mail: aserpenguzel@ku.edu.tr
Office hours: Monday-Wednesday 13:30 - 15:00
Teaching assistant: Bilgin Ersoy
Office: A-105
Ext: 657
e-mail: bersoy@ku.edu.tr
Office hours: TBA
Lectures: Monday-Wednesday 10:30 - 12:00
Course contents:
Introduction
to semiconductors: crystals,
energy bands, charge carriers and doping, the Fermi Level, carrier
lifetime
and mobility, and optical properties. Electronic devices: p-n junction,
diodes, transistors; optoelectronic devices: light emitting diodes
(LED's),
diode lasers, and detectors.
Required Textbook: M.S. Tyagi, "Introduction to Semiconductor
Materials and Devices," Wiley, New York (1991).
Recommended Textbooks: P. Bhattacharya, "Semiconductor
Optoelectronic
Devices," Prentice Hall, New Jersey (1997).
A. M. Ferendeci, "Physical Foundations of Solid State and Electron
Devices,"
Mc Graw Hill, New York (1991).
S. M. Sze, "Semiconductor Devices: Physics and Technology," Wiley, New
York (1985).
S. M. Sze, "Physics of Semiconductor Devices," Wiley, New York
(1981).
S. M. Sze (Editor), Modern Semiconductor Device Physics, Wiley, New
York
(1998).
Attendance: Attendance will be taken in the lectures. Students are required to attend all classes and problem sessions. Participation in classes and problem sessions will be taken into consideration in determining the grades of borderline students.
Grading policy: 2 midterm exams (25 % each), final exam (40 %), homeworks and quizzes (10%).
The date of the midterms and the final exam will be announced later. Makeup exams are very reluctantly given only with a university approved medical excuse, and if given, will always be harder then the original exams. Do not plan to take makeups.
Homework problems will be posted on the network. You can always ask the instructor s or assistants for help with the suggested problems as well as other problems. Students are advised to do more problems than are listed: physics is best learned by working on the problems.
Academic honesty: Academic dishonesty including cheating on the exams, laboratory reports, quizzes, and homework is a serious offense, and will not be tolerated. University policy regarding this matter will be fully enforced. Please read the section on academic honesty in the university catalogue. If you have further questions, ask your advisor or instructor for assistance.
Most of our daily life revolves around electronic (and optoelectronic, photonic) equipment, such as radios, phones, scanners, copiers, etc. At the heart of these devices are semiconductors. Since, we are moving from the electronics age to the optoelectronics (or photonics) age, a graduating science or engineering major should be equipped with the knowledge of how semiconductor and semiconductor devices work. Here are some important questions about the content of the course.
Why should we study semiconductor physics and devices?
What are semiconductors? Materials, such as silicon and germanium, whose electrical properties lie between those of conductors (such as metals) and insulators (such as glass and rubber). Semiconductors exhibit relatively high resistance in a pure state and much lower resistance when they contain small amounts of certain impurities.
What is a crystal? Crystals are built out of atoms. The fundamental building blocks for atoms are protons, neutrons and electrons. Atoms are listed and arranged in the periodic table according to their number of protons (increasing left to right across the rows).
What are the energy bands? The energy bands are the energy levels that are occupied by the charge carriers (electrons and holes). In semiconductors, there is a valence band and a conduction band. The "band gap" energies are forbidden to both carriers.
What are charge carriers? Electrons and holes: An electron is an elementary atomic particle that carries the smallest negative electric charge (1.6x10-19 coulombs). Electrons are light in mass, (1/1837 of the mass of the hydrogen atom), highly mobile, and orbit the nucleus of an atom. A hole is a mobile electron vacancy in a semiconductor that acts like a positive electron charge (+1.6x10-19 coulomb) with a positive mass. Unoccupied spot among the electrons that are bound in their orbits. Under the application of an electric field, holes move in the opposite direction from electrons, thereby producing an electric current. Holes are induced into an integrated circuit by adding small quantities of an acceptor dopant to the host silicon crystal.
What is the Fermi Level? The Fermi level is an energy level below (above) which all the electron states are full (empty) at absolute zero temperature.
What is the carrier lifetime? The carrier lifetime is the time during which the charge carriers (electrons and holes) exist in the semiconductor material before recombination occurs.
What is mobility? The mobility is the velocity of a charged carrier attained under the action of an applied electric field. Units are cm2/V-Sec.
What are the optical properties of semiconductors? Depending on their crystal structure and electronic properties semiconductors absorb, emit, and transmit light at different wavelengths. These optical properties are used in the design of optoelectronic elements.
What is doping? The intentional introduction of a selected chemical impurity (dopant) into the crystal structure of a semiconductor to modify its electrical properties. For example, adding boron to silicon makes the material more P-type. Doping concentrations range from a few parts per billion (for resistive semiconductor regions) to a fraction of a percent (for highly conductive regions).
What is a semiconductor device? An electronic device whose essential characteristics are governed by the flow of charge carriers within a semiconductor. A class of electronic components, such as power MOSFETs, bipolar power transistors, surgectors, MOVs, optoelectronic devices, rectifiers, power hybrid circuits, intelligent power discretes, and transistors. Typically, these devices contain one active element, such as a transistor or diode. However, hybrids, optoelectronic devices, and intelligent discretes may contain more than one active element. In contrast, integrated circuits (ICs) typically contain hundreds, thousands, or even millions of active elements in a single die.
What is a P-N junction? A P-N junction is an interface plane within a semiconductor crystal, at which the number of P- and N-type carriers are exactly equal, with a surplus of P-type on one side of the junction and N-type on the other.
Solid State Radio (uses diodes and transistors)
What is a diode? A diode is a two-terminal semiconductor device that exhibits a non-linear current-voltage characteristic. The function of a diode is to allow current in one direction and to block current in the opposite direction. The terminals of a diode are called the anode and cathode. There are two kinds of semiconductor diodes: a P-N junction diode, which forms an electrical barrier at the interface between N- and P-type semiconductor layers, and a Schottky diode, whose barrier is formed between metal and semiconductor regions.
What is a transistor? A transistor is a three-terminal active semiconductor device that provides current amplification. A bipolar transistor is comprised of base, emitter and collector and is a current-controlled device with a low input impedance. A field-effect transistor has gate, source, and drain electrodes and is a high-impedance, voltage controlled device. The first transistor was invented at Bell Laboratories in 1947 by physicists John Bardeen, William B. Shockley and Walter Brattain, who shared the 1956 Nobel Prize for jointly inventing the transistor, a solid-state device that could amplify electrical current. The transistor performed electronic functions similar to the vacuum tube in radio and television, but was far smaller and used much less energy. The transistor became the building block for all modern electronics and the foundation for microchip and computer technology.
What is an optoelectronic device? An optoelectronic device is a device that is responsive to or that emits or modifies light waves. Examples are LED's, optical couplers, laser diodes, and photo detectors.
What is a light emitting diode (LED)? A light emitting diode is a semiconductor P-N junction diode that emits light under forward-bias conditions. The wavelength of the emitted light is a function of the semiconductor material. The crystal structure of silicon does not provide useful levels of light emission, but the structure of GaAs does, with an infrared emission wavelength.
What is a diode laser? A diode laser is also a semiconductor P-N junction diode that emits light under forward-bias conditions. The wavelength of the emitted light is a function of the semiconductor material. The crystal structure of silicon does not provide useful levels of light emission, but the structure of GaAs does, with an infrared emission wavelength. If we wanted to draw an analogy between the solid state and the gaseous device, the LED would be the analogue of the neon lamp, while the diode laser would be the analogue of a Helium Neon (He-Ne) laser.
Diode lasers continue to find new product applications as the lasing wavelength is pushed lower into the visible spectrum. The latest generation of the visible diode lasers operate around 635 nm (this wavelength being similar to a He-Ne gas laser) is highly visible to the human eye. Visible diode lasers in the range from 635 nm to 690 nm are replacing the traditional He-Ne laser in many commercial products for good reasons: lower cost, compact size, and superior long-term reliability. Another intrinsic benefit of diode lasers is that these lasers are generally better suited for battery operated devices and other low voltage applications. While visible diode lasers are used extensively in commercial products, the near infrared diode lasers are certainly not extinct. There are many applications still using lasers operating in the 780 nm ~ 850 nm range as some machine vision systems and sensors are optimized for near infrared light sources.
What is a semiconductor detector? There are various types of semiconductor photodetectors: photoconductors, photodiodes, and avalanche photodiodes. In all of these devices, charge carriers are generated by light, charge carriers are transported (and/or multiplied) by an electrical current, and the photocurrent is detected to produce an electrical signal.