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Materials

Materials. Conductive materials – valence band overlaps the conduction band Non conductive materials – valence band is separated from conduction band and electrons can not easily get to the conduction band

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Materials

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  1. Materials • Conductive materials – valence band overlaps the conduction band • Non conductive materials – valence band is separated from conduction band and electrons can not easily get to the conduction band • Semiconductor materials – conduction band is close to valence band and electrons can easily jump from the valence band to the conduction band with an energy source

  2. Silicon is an element Silicon is the first or second most abundant element on the earth Sand is a form of silicon Silicon is know as a semiconductor because under certain conditions it can conduct electricity (electrons) Silicon is the most widely used material for today’s microelectronics Silicon was not the first semiconductor material used, germanium was first. Silicon

  3. Group 4

  4. Silicon • From the periodic chart you can see that silicon is a group 4 element • Group 4 elements have 4 electrons in their outer most electron shell • Silicon is the most common material currently used for solar cells

  5. Why is silicon an excellent microelectronics material? • It is very abundant • It can be grown into a single orientation crystal • It can be made electrically active easily • It can be made to conduct electrons with a small applied potential • It has a naturally forming oxide that acts as an insulating and diffusion barrier

  6. Silicon ingot ready to be cut into wafers

  7. Silicon ingot being grown

  8. Two dimensional schematic of three dimensional crystal

  9. Group 3 Elements

  10. P type doping – Positive, electron short, also called a hole

  11. Group 5 elements

  12. N-type doping – N is negative, electron rich

  13. Combing n-type silicon and p-type silicon gives a pn junction

  14. Silicon crystal planes and Miller Index

  15. Silicon wafers have “flats” to denote what type of wafer it is

  16. The future Silicon will continue to play a dominant role but other semiconductor materials will play an increasing role III-V semiconductor materials made from group III and group V elements are now common ( GaAs, InP, AlN ) II-VI semiconductor materials are being investigated for special applications SiC, “diamond like carbon”, and SiGe are also of interest

  17. Assignment Submit a schedule of times you can work in the clean room Must be at least a 2 hour time block You can work with a friend but each student will be required to build their own solar cell

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