The direction of electric field when the gate voltage is zero:a)Metal ...
Metal being more positive compared to semiconductor.. Electric field exists from metal to semiconductor.
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The direction of electric field when the gate voltage is zero:a)Metal ...
Understanding Electric Field Direction at Zero Gate Voltage
When the gate voltage in a metal-semiconductor junction is zero, the behavior of the electric field is largely determined by the properties of the materials involved. Here’s a detailed breakdown of why the electric field direction is from metal to semiconductor.
Basic Concepts
- In a metal-semiconductor junction, the metal typically has a higher work function compared to the semiconductor.
- The work function is the minimum energy needed to remove an electron from the surface of a material.
Band Alignment at Zero Gate Voltage
- When the gate voltage is zero, the energy bands of the metal and semiconductor align due to the difference in work functions.
- Electrons from the semiconductor will flow towards the metal side, creating a depletion region near the semiconductor surface.
Electric Field Direction
- As electrons move from the semiconductor to the metal, a positive charge builds up in the semiconductor near the junction.
- According to the convention of electric fields, they point from positive to negative. Therefore, the electric field direction is from the positively charged metal (due to the absence of electrons) to the negatively charged semiconductor.
Conclusion
- Thus, when the gate voltage is zero, the electric field exists and is directed from the metal to the semiconductor. This understanding is crucial in the design and analysis of devices like MOSFETs, where gate voltage plays a significant role in controlling the electric field and, consequently, the flow of current.
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