EASA Module 4 atomic structure

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The slide is used for classroom lecture for module 4 of EASA B1.1 license course. Part of the module to unable student to understand how semi conductor works

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EASA Module 4 atomic structure

  1. 1. MODULE 4.1Semiconductors
  2. 2. Syllabus Part 66 Module 4.1 (B1.1 Excluded) (B2 – Level 2) Materials, electron configuration, electrical properties; P and N type materials: effects of impurities on conduction, majority and minority characters; PN junction in a semiconductor, development of a potential across a PN junction in unbiased, forward biased & reverse biased conditions;
  3. 3. Comments on Syllabus Although it is not included, however, without knowledge of the semiconductor, a student will not be able to understand how a diode or transistor works. Due to this requirement, the subject is included in the program.
  4. 4. Introduction Modern Electronics ◦ 19th Century – Thomas Edison discovered heated metal emitted charged particles.  Led to discovery of thermionic valve. ◦ 1940 – transistor was invented by Bell Laboratories ◦ 1950s’ – development of integrated circuit ◦ 1960s – prediction that the number of transistors in IC would be doubled every 18 months. ◦ 2007 – an advanced IC contained 55 mil transistors
  5. 5. Atomic Structure ◦ 1913 – Bohr – Beginning of the basic theory of atomic structure.
  6. 6. Valence Shell The tendency of atoms to gain or loss electrons depends on the number of electrons in the outmost shell. The outmost shell is known as valence shell and the electrons is known as valence electrons.
  7. 7. Energy Bands x-axis- the allowed energy levels numbered from 1 to 5. The y-axis shows each levels energy in electron volts (eV) One electron volt is the energy that an electron gains when it travels through a potential difference of one volt (1 eV = 1.6 x 10-19 Joules).
  8. 8. Energy in Atoms As in previous slide, the energy level is discreet. Electrons are in either conduction bands or valence band. Materials with large amount of electrons in the conduction bands are good conductor.
  9. 9. Atoms of semiconductors Silicon  Germanium
  10. 10. Covalent Bonding Single Atom Crystallize Structure/ lattice
  11. 11. Semi Conductor N Type P Type
  12. 12. Electron Flow Hole FlowDoped with Arsenic Conduction Intrinsic flow – there is no impurities added
  13. 13. Doping Process … A pure silicon or germanium are insulator. It has valence electrons of 4. Adding impurities will change the characteristic of the semiconductor. If elements with 5 valent electrons is added, it will have one electron balance, thus become N-type, negative type with electrons as the current carrier.
  14. 14. … Doping Process If an element with 3 electrons is added, then it will be P-type with holes. P type or positive type will conduct current via holes, similar to the conventional flow of current. Example of impurities for N-types are arsenic and phosphorous. Example of impurities with 3 valent electron and used to manufacture P type semiconductor is boron, gallium and indium.
  15. 15. N-type semiconductor The doping is done by 5 valence electrons – pentavalent impurity. ◦ Example arsenic, antimony, bismuth and phosphorous.
  16. 16. P-Type Semiconductor Doping with impurities with 3 valence electrons or trivalent will produce a P- type semi-conductor. ◦ Example of trivalent materials are – alluminium, indium, gallium, boron ◦ Concept of minor and major carriers.
  17. 17. RESOURCES My Blog Recommended Books Title Autho ISBN r Aircraft Electricity Eisma 0-02- and Electronics n 801859-1 Art of Horowi 0-521- tz /Hill 37095-7 Electronics Horowitz /Hill Elements of Hickey/ 0070286957 Villines Electronics Modern Aviation Helfric 0-13-118803- Electronics h 8 Micro E 0-273- Electronics in Pallet 08612-X Aircraft systems

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