PN Junction Diode: Forward Biasing
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Questions and Answers

What is the result of the transfer of free electrons from the n-type semiconductor into metal near the contact?

  • Energy band flattening
  • Energy band bending (correct)
  • Energy band widening
  • Energy band straightening
  • What happens to the potential barrier ΦB across the semiconductor when the Fermi energy of metal becomes lower than the Fermi energy in the semiconductor?

  • It increases
  • It reduces (correct)
  • It remains constant
  • It becomes zero
  • What is the direction of the current generated across the MS junction under forward biasing?

  • From metal to semiconductor
  • It is zero
  • No current is generated
  • From semiconductor to metal (correct)
  • What happens to the depletion region as the applied voltage is continuously increased under forward biasing?

    <p>It becomes very thin and finally disappears</p> Signup and view all the answers

    What is the direction of the applied bias on the metal in reverse biasing?

    <p>Negative</p> Signup and view all the answers

    What is the purpose of the LED series resistance in reverse biasing?

    <p>To limit the current</p> Signup and view all the answers

    What is the primary characteristic of the Schottky barrier?

    <p>Surface potential-energy barrier</p> Signup and view all the answers

    Where is the built-in-voltage primarily present?

    <p>Primarily inside the n-type semiconductor</p> Signup and view all the answers

    What is the result of the net loss of electrons at the metal-semiconductor interface?

    <p>A depletion region and a growing barrier at the semiconductor surface</p> Signup and view all the answers

    What is the energy required for electrons to flow from the n-type semiconductor to the metal?

    <p>Greater than the built-in-voltage</p> Signup and view all the answers

    What is the width of the region where electrons move into the metal compared to the width inside the n-type semiconductor?

    <p>Negligibly thin</p> Signup and view all the answers

    What occurs when the Schottky diode is unbiased?

    <p>Only a small number of electrons flow from the n-type semiconductor to the metal</p> Signup and view all the answers

    What happens to a ferromagnetic substance when it is inserted in a current-carrying coil?

    <p>It becomes magnetized</p> Signup and view all the answers

    What is the term for the process of demagnetizing a substance by reversing the direction of the current?

    <p>Hysteresis</p> Signup and view all the answers

    What happens to the magnetic flux density (B) when the magnetic field strength (H) is increased from zero to one?

    <p>B increases</p> Signup and view all the answers

    What is the point where the value of magnetism remains constant even when the magnetic field is increased?

    <p>Saturation point</p> Signup and view all the answers

    What is the term for the amount of force required to remove a material's retentivity?

    <p>Coercive force</p> Signup and view all the answers

    What is the result of hysteresis in electric machines' ferromagnetic cores?

    <p>Energy loss</p> Signup and view all the answers

    Study Notes

    Schottky Barrier

    • The net loss of electrons creates a negative charge in the metal and a positive charge in the semiconductor, resulting in a depletion region and a growing barrier at the semiconductor surface.
    • The equilibrium band structure for a metal and a n-type semiconductor is characterized by the Schottky barrier height, ΦB, which is a function of the metal and the semiconductor: ΦB = ΦM - χ.
    • The built-in-potential or built-in-voltage is primarily present inside the n-type semiconductor, preventing further electron flow from the semiconductor conduction band into the metal.

    Forward Biasing

    • Under a forward biasing (VA > 0), the Fermi energy of metal becomes lower than the Fermi energy in the semiconductor, EF, reducing the potential barrier ΦB across the semiconductor.
    • This makes it easier for electrons to pass over the barrier, allowing them to diffuse from semiconductor to metal, resulting in a positive current.
    • As the applied voltage increases, the depletion region becomes thinner and finally disappears.

    Reverse Biasing

    • With a negative applied bias on the metal (VA < 0), the potential barrier ΦB increases, making it more difficult for electrons to overcome the surface barrier.
    • The depletion region becomes wider, and the current decreases.

    Hysteresis Loop

    • The hysteresis loop is formed by continuously monitoring the magnetic flux released by the ferromagnetic substance as the external magnetizing field is altered.
    • The loop is characterized by the saturation point, retentivity point, and coercive force.
    • The hysteresis loop is a cycle of magnetization and demagnetization, with the material retaining some magnetic retentivity, even when the magnetic field is zero.
    • Hysteresis can cause energy loss in electric machines' ferromagnetic cores.

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    Description

    This quiz covers the concept of forward biasing in Metal-Semiconductor (MS) junctions, including the energy band bending and reduction of potential barrier. It's a fundamental topic in electronics and semiconductor physics. Test your understanding of the PN junction diode operation under forward biasing.

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