Introduction to Schottky Diode and Semiconductor Switch
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Questions and Answers

What is a characteristic of a Schottky diode?

  • Slow switching speed
  • High current resistance
  • High forward voltage drop
  • Low forward voltage drop (correct)

    • What type of contact is formed when a metal and a semiconductor are joined?

  • Ohmic contact only
  • Rectifying contact only
  • Either rectifying or ohmic contact (correct)
  • Neither rectifying nor ohmic contact

    • What is the Fermi Level?

  • The highest energy level that an electron can occupy (correct)
  • The lowest energy level that an electron can occupy
  • The energy level between the valence and conduction bands
  • The energy level at which all electrons exist

    • What is the purpose of a band diagram in understanding Schottky diodes?

    <p>To illustrate the energy level of electrons</p> Signup and view all the answers

    What is the result of applying a forward voltage to a Schottky diode?

    <p>Current flow in the forward direction</p> Signup and view all the answers

    What is the name of the contact formed between a metal and a semiconductor?

    <p>Schottky barrier contact</p> Signup and view all the answers

    What is the energy difference between the conduction band minimum and the vacuum energy level?

    <p>Electron affinity</p> Signup and view all the answers

    What is the term for the energy required to take an electron from the Fermi level and give it enough energy to escape to infinity?

    <p>Work function</p> Signup and view all the answers

    What is the type of contact used in a Schottky diode for switch applications?

    <p>Unipolar contact</p> Signup and view all the answers

    What is the symbol used to represent the work function in semiconductors?

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

    What is the location of the Fermi level in a n-type semiconductor?

    <p>Close to the conduction band</p> Signup and view all the answers

    What is the purpose of a Schottky diode when used as a rectifier contact?

    <p>To allow current flow in one direction</p> Signup and view all the answers

    What is the primary characteristic of the Schottky barrier?

    <p>Barrier height</p> Signup and view all the answers

    What is the result of electrons transferring from the semiconductor to the metal under equilibrium conditions?

    <p>A negative charge in the metal and a positive charge in the semiconductor</p> Signup and view all the answers

    What is the role of the built-in-voltage in a Schottky barrier?

    <p>To prevent the movement of electrons from the semiconductor to the metal</p> Signup and view all the answers

    What is the relationship between the Schottky barrier height and the Fermi energy of the metal?

    <p>ΦB = ΦM - χ</p> Signup and view all the answers

    Why is the width of the depletion region primarily present inside the n-type semiconductor?

    <p>Because the metal has a sea of free electrons</p> Signup and view all the answers

    What is necessary for the conduction band electrons of the n-type semiconductor to overcome the built-in-voltage?

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

    What is the primary characteristic of a Schottky barrier?

    <p>It is a depletion layer formed at the metal-semiconductor junction</p> Signup and view all the answers

    What happens when a metal and a semiconductor material are brought together?

    <p>An instant ideal MS contact is formed without electron movement</p> Signup and view all the answers

    What is the significance of the work function of semiconductors?

    <p>It is related to the electron affinity and the conduction band</p> Signup and view all the answers

    What is the condition for the formation of a Schottky contact?

    <p>φm  φs</p> Signup and view all the answers

    What is the function of a Schottky barrier in a diode?

    <p>It is the potential energy barrier that electrons must overcome to flow across the diode</p> Signup and view all the answers

    What is the type of semiconductor that can form a Schottky contact?

    <p>Both n-type and p-type semiconductors</p> Signup and view all the answers

    What is the primary reason that prevents further electron flow from the n-type semiconductor to the metal in an unbiased Schottky diode?

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

    What happens to the potential barrier across the semiconductor when a forward bias is applied to the MS junction?

    <p>It decreases</p> Signup and view all the answers

    What is the direction of the current generated across the MS junction when a forward bias is applied?

    <p>From the semiconductor to the metal</p> Signup and view all the answers

    What happens to the depletion region when the applied voltage is continuously increased in a forward-biased MS junction?

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

    What is the effect of the reduction of the potential barrier on the flow of electrons across the MS junction?

    <p>It makes it easier for electrons to pass over the barrier</p> Signup and view all the answers

    What is the result of the transfer of free electrons from the n-type semiconductor to the metal in an unbiased Schottky diode?

    <p>Energy band bending near the contact</p> Signup and view all the answers

    Study Notes

    Fermi Level and Energy Bands

    • Fermi level changes as solids are warmed and electrons are added to or withdrawn from the solid
    • Fermi level lies close to the conduction band and valence band in a n-type and p-type semiconductor

    Work Function

    • Measures the energy required to take an electron from the Fermi energy level to infinity (vacuum) with zero energy
    • Represented as Фm for metals and Фs for semiconductors
    • Measured in terms of voltage

    Electron Affinity

    • Measures the energy required to capture an electron and convert it to a negatively charged ion
    • Energy difference between the conduction band minimum (CBM) and the vacuum energy level
    • Denoted by χ and measured in terms of voltage

    Schottky Diode

    • A type of metal-semiconductor diode with a low forward voltage drop and fast switching speed
    • Formed by joining a metal and a semiconductor, resulting in a rectifying contact (Schottky barrier contact)
    • Allows current to flow in one direction when enough forward voltage is applied

    Schottky Barrier

    • A depletion layer formed at the junction of a metal and n-type semiconductor
    • Potential energy barrier that electrons must overcome to flow across the diode
    • Characterized by the Schottky barrier height, ΦB = ΦM - χ, for n-type semiconductor

    Working of a Schottky Diode

    • Under equilibrium conditions, electrons transfer from the semiconductor to the metal, creating a depletion region and a growing barrier
    • The built-in-potential (built-in-voltage) is primarily present inside the n-type semiconductor
    • To overcome the barrier, free electrons need energy greater than the built-in-voltage

    Forward Biasing

    • When the applied voltage is increased (VA > 0), the Fermi energy of the metal becomes lower than the Fermi energy in the semiconductor
    • The potential barrier ΦB across the semiconductor is reduced, making it easier for electrons to pass over the barrier
    • The current increases rapidly as more electrons diffuse from the semiconductor to the metal

    Reverse Biasing

    • When the applied bias is negative (VA < 0), the depletion region becomes wider, and the current decreases

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    Description

    Learn about the Schottky Diode, a type of metal-semiconductor diode with low forward voltage drop and fast switching speed. Understand the two possible types of contact between metal and semiconductor, including rectifying and ohmic contacts.

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