EEE-201Lecture 2 www.fida.com.bd
EXTRINSIC MATERIAL• The characteristic of semiconductor can  be altered by adding impurity through  doping process (extrin...
N-TYPE• N-type is created by  introducing impurity elements  that have five valence  electrons (pentavalent) –  antimony, ...
P-TYPE• P-type is created by doping  with impurity atoms having  three valence electrons –  boron gallium, indium• Note th...
Electron versus Hole Flow          www.fida.com.bd
Majority and Minority Carriers• In an n-type material - electron is called majority  carrier and hole the minority carrier...
Semiconductor Diode•   Diode is formed by bringing these two material together p- and    n-type•   Electrons and holes at ...
• Since the diode is two-terminal device,  the application of a voltage across its  terminals leaves three possibilities: ...
No Applied Bias (VD = 0V)•   Under no-bias conditions, any minority carries (holes) in the n-type    material find themsel...
Figure 1.14 p-n junction with no external bias                 www.fida.com.bd
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Reverse-Bias Condition (VD < 0V)• The number of uncovered positive ions in the depletion  region of n-type will increase d...
Figure 1-16 Reverse-biased p-n junction              www.fida.com.bd
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Forward-Bias Condition (VD = 0V)• A semiconductor diode is forward-biased when the  association p-type and positive and n-...
Figure 1.18 Forward-biased p-n junction               www.fida.com.bd
For Forward-bias and Reverse-bias                                         (1.4)                       www.fida.com.bd
Figure 1.19 Silicon semiconductor diode characteristics                       www.fida.com.bd
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EEE201 LECTURE 2~www.fida.com.bd

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  • EEE201 LECTURE 2~www.fida.com.bd

    1. 1. EEE-201Lecture 2 www.fida.com.bd
    2. 2. EXTRINSIC MATERIAL• The characteristic of semiconductor can be altered by adding impurity through doping process (extrinsic material)• Two type: – N-type – P-type www.fida.com.bd
    3. 3. N-TYPE• N-type is created by introducing impurity elements that have five valence electrons (pentavalent) – antimony, arsenic, phosphorus• Note that four covalent bonds are still present, however there is additional fifth electron due to impurity atom• The remaining electron is free to move within the newly formed n-type material• Diffused impurities with five Figure 1.9 Antimony valence electrons are called impurity in n-type material donor atoms www.fida.com.bd
    4. 4. P-TYPE• P-type is created by doping with impurity atoms having three valence electrons – boron gallium, indium• Note that there are insufficient number of electrons to complete covalent bonds resulting a hole• This hole is ready to accept a free electron• The diffused impurities with three valence electrons are Figure 1.11 Boron impurity called acceptor atoms. in p-type material www.fida.com.bd
    5. 5. Electron versus Hole Flow www.fida.com.bd
    6. 6. Majority and Minority Carriers• In an n-type material - electron is called majority carrier and hole the minority carrier• In a p-type material – hole is majority carrier and electron is the minority carrier www.fida.com.bd
    7. 7. Semiconductor Diode• Diode is formed by bringing these two material together p- and n-type• Electrons and holes at joined region will combine, resulting in a lack of carriers in the region near the junction (depletion region) www.fida.com.bd
    8. 8. • Since the diode is two-terminal device, the application of a voltage across its terminals leaves three possibilities: – No bias (VD = 0V) – Foreard bias (VD > 0V) – Reversed bias (VD < 0V)• Each condition will result in a response www.fida.com.bd
    9. 9. No Applied Bias (VD = 0V)• Under no-bias conditions, any minority carries (holes) in the n-type material find themselves within the depletion region will pass directly into p-type material• Majority carriers (electrons) of n-type material must overcome the attractive forces of the layer of positive ions in n-type material and the shield of negative ions in p-type material to migrate into the area beyond the depletion region of p-type material.• In the absence of an applied bias voltage, the net flow of charge in any one direction for semiconductor diode is zero www.fida.com.bd
    10. 10. Figure 1.14 p-n junction with no external bias www.fida.com.bd
    11. 11. www.fida.com.bd
    12. 12. Reverse-Bias Condition (VD < 0V)• The number of uncovered positive ions in the depletion region of n-type will increase due to large number of free electrons drawn to the positive potential• The number of uncovered negative ions will increase in p- type resulting widening of depletion region• This region established great barrier for the majority carriers to overcome – resulting Imajority = 0• The number pf minority carriers find themselves entering the depletion region will not change resulting in minority- carrier flow vectors of the same magnitude• The current exists under reverse-bias conditions is called the reverse saturation current and represented by Is• Therefore, ID= -Is www.fida.com.bd
    13. 13. Figure 1-16 Reverse-biased p-n junction www.fida.com.bd
    14. 14. www.fida.com.bd
    15. 15. Forward-Bias Condition (VD = 0V)• A semiconductor diode is forward-biased when the association p-type and positive and n-type and negative has been established• The application of forward-bias potential will pressure the electrons in n-type and hole in p-type to recombine with ions near the boundary and reduce the width of depletion region• The resulting minority-carrier flow of electrons from p- type to n-type has not changed in magnitude, but the reduction in width of depletion region has resulted in a heavy majority flow across the junction www.fida.com.bd
    16. 16. Figure 1.18 Forward-biased p-n junction www.fida.com.bd
    17. 17. For Forward-bias and Reverse-bias (1.4) www.fida.com.bd
    18. 18. Figure 1.19 Silicon semiconductor diode characteristics www.fida.com.bd
    19. 19. www.fida.com.bd
    20. 20. www.fida.com.bd

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