Diese Präsentation wurde erfolgreich gemeldet.
Wir verwenden Ihre LinkedIn Profilangaben und Informationen zu Ihren Aktivitäten, um Anzeigen zu personalisieren und Ihnen relevantere Inhalte anzuzeigen. Sie können Ihre Anzeigeneinstellungen jederzeit ändern.

Semiconductor fundamentals

975 Aufrufe

Veröffentlicht am


Veröffentlicht in: Wissenschaft
  • Als Erste(r) kommentieren

Semiconductor fundamentals

  1. 1. Semiconductor Fundamentals Dr. M. Yousuf Soomro Semiconductors Fundamentals
  2. 2. Course Outline To understand the semiconductor materials that are suitable for electronic devices To study the properties of materials for electronic devices Semiconductor devices are fabricated using specific materials has the desired physical properties
  3. 3. Solid State Materials Metals (conductor) Insulators Semiconductors Superconductors
  4. 4. Metals Materials with zero bandgap are metals A metal has a partially filled conduction band, so there is no energy gap between filled and unfilled regions. A significant number of electrons can be excited by heat into empty energy levels and move easily throughout the material, allowing the material to conduct electricity
  5. 5. Insulators Materials with an energy gap larger than 3 eV An insulator possesses a considerable energy gap between the valence band and the conduction band It is difficult to excite electrons from the valence band to the conduction band. As a result an insulator does not conduct electricity
  6. 6. Semiconductor Special class of materials having conductivity b/w that of a good conductor and that of an insulator A material with electrical resistivity lying in the range of 10-2 – 109 Ω.cm Material whose energy gap for electronic excitations lies between zero and about 4 electron volts (eV). a small number of electrons from the valence band can be promoted to the conduction band by an energy input (e.g. thermal energy from heat)
  7. 7. Semiconductor Classification of Semiconductor materials oElemental semiconductor oCompound semiconductor oNarrow band-gap semiconductor oWide band-gap semiconductor oOxide semiconductor oMagnetic semiconductor oOrganic semiconductor oLow dimension semiconductor
  8. 8. Semiconductor Elemental semiconductor Silicon (Si) Germanium (Ge) o These are important group IV elemental semiconductors o All of them have diamond crystal structure Boron (B) o It belongs to group III o It has rhombohedral crystal structure Phosphorus (P) o It belongs to group V Sulphur (S) Selenium (Se) Tellurium (Te) o These belong to group VI
  9. 9. Semiconductor  Elemental semiconductor Currently silicon is the most important semiconductor material used in electronic devices Advantages of Si over other semiconductors are: A relative ease of passivating the surface by oxidizing in a controlled manner forming a layer of stable native oxide that substantially reduces the surface recombination velocity Its hardness that large wafers to be handled safely without damaging it It is thermally stable up to 11000C that allows high- temperature processes like diffusion, oxidation, and annealing It is relatively low cost due to established processes
  10. 10. Semiconductor  Elemental semiconductor  limitations of silicon Its energy band-gap is 1.12eV It is a direct semiconductor that limits the application in optoelectronics It has relatively low carrier mobility as compared to other semiconductor such as gallium arsenide GaAs
  11. 11. Semiconductor Compound Semiconductors They are usually formed from o III-V group o II-VI o IV-VI III-V group semiconductors are GaAs, GaP, GaN, A1As, InSb, InAs, InP etc In general, these crystallized materials
  12. 12. Semiconductor Compound Semiconductors GaAs, InAs, InP, InSb have direct energy band-gaps and high carrier mobilities Common applications of these semiconductors:  used to design a variety of optoelectronic devices for 1. detection and generation of electromagnetic radiation 2. in high-speed electronic devices The energy band-gaps of these compounds are useful for optoelectronic applications The energy bandgap ranges from 0.17eV for InSb to 3.44eV for GaN
  13. 13. Semiconductor Compound Semiconductors II-VI compound semiconductor II-VI compound semiconductor such as Zn and compounds with oxygen O, S, Se These cover a wide range of electronic and optical properties due to the wide variations in their energy bandgap These are typically n-type as grown, except ZnTe, which is p- type All the II-VI compound semiconductors have direct energy bandgaps
  14. 14. Semiconductor Compound Semiconductors IV-VI compound semiconductor PbS, PbSe, and PbTe characterized by narrow energy gaps, high carrier mobilities, and high dielectric constants The unique feature of the direct energy gap in these compounds is that its energy band-gap increases with increasing temperature, which means the energy gap has a positive temperature coefficient Main applications of these compounds are in light emitting devices and detectors in the infrared spectral region
  15. 15. Semiconductor Narrow Band-gap Semiconductor  InSb  InAs  PbSe  PbTe  PbS They have the energy band-gap below about 0.5eV they are direct semiconductor materials extensively employed in: infrared optoelectronic device applications as detectors and diode lasers
  16. 16. Semiconductor Wide Band-gap Semiconductor  SiC  II-V nitrides high thermal conductivity high saturation electron drift velocity high breakdown electric field superior chemical stability physical stability It has wide band-gap that enables detection and emission of light in short-wavelength region likes blue and ultraviolet
  17. 17. Semiconductor Oxide Semiconductor  Cu2O  Bi2O  ZnO These are also referred as semiconductor ceramics They are used in electronic devices and sensors
  18. 18. Semiconductor Magnetic Semiconductor Semiconductor compound that contains magnetic ions such as Cr, Mn, Fe, Co, Ni, may exhibit magnetic properties Some oxides such as FeO and NiO exhibit antiferromagnetic properties and oxide such as europium oxide EuO is ferromagnetic properties The semiconductor exhibits large magneto-optical effect that can be used to design optical modulators
  19. 19. Semiconductor Organic Semiconductor  Anthracene CH14H10  Polyacetylene (CH)n  advantages of organic semiconductors 1. Diversity 2. relative ease of changing their properties to specific application
  20. 20. Semiconductor Organic Semiconductor One of the promising applications of organi semiconductors is in less iexpensive light emitting diode, covering whole the spectrum of colors The main advantages of organic materials in such applications include I. low operating voltages II. color tunability III. relative simplicity of device fabrication