Field and Potential in P-N junction

References: NCERT Class 12, Chapter 14, Semiconductor Electronics: Materials, Devices, and Simple Circuits

Important subtopics:

• Formation of depletion layer:

• Formation of P-N junction by joining N-type and P-type semiconductors

• Diffusion of majority carriers across the junction

• Establishment of equilibrium and formation of depletion layer

• Built-in potential:

  • Definition of built-in potential (Vbi)
  • Calculation of built-in potential using Fermi level difference and contact potential
  • Significance of built-in potential in P-N junction

• Electric field in the depletion region:

• Gauss’s law in the depletion region

• Derivation of electric field (E) in the depletion region

• Variation of electric field with distance

• Potential variation across the depletion region:

• Derivation of potential variation (V) across the depletion region

• Relationship between potential variation and electric field

• Graphical representation of potential variation

• Capacitance of P-N junction:

• Definition of capacitance (C) in P-N junction

• Derivation of capacitance using charge-voltage relation and plate separation

• Factors affecting capacitance:

  • Doping concentration (N)
  • Depletion region width (w)
  • Junction area (A)

• Applications of P-N junction diode:

• Rectifier:

  • Principle of rectification: conversion of alternating current (AC) to direct current (DC)

  • Half-wave rectifier:

    • Circuit diagram and working
    • Output waveform

  • Full-wave rectifier:

    • Circuit diagram and working
    • Output waveform
    • Bridge rectifier:
      • Circuit diagram and working
      • Output waveform

• Zener diode:

  • Zener breakdown:

    • Mechanism of Zener breakdown
    • Comparison with avalanche breakdown

  • Voltage regulation using Zener diode:

    • Circuit diagram and working
    • Load regulation and line regulation

Additional resources:

• Semiconductor Devices: Basic Principles by S. M. Sze
• Electronic Devices and Circuits by Jacob Millman and Christos Halkias
• Fundamentals of Solid-State Electronics by Ben Streetman and Sanjay Banerjee