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PN JUNCTION (Application (Switches in digital logic designs, Rectifiers in…

- - - - PN Junction
        
        P-type material is formed by the addition of impurity with trivalent doping material like Boron
        
        N-type material is formed by the addition of pentavalent doing material like Antimony
  - - - Metal Semiconductor Junction
- - - - Positive charge is left in the n region and negative charge is created in the p region (forming barrier potential)
      - This action continues until the voltage of the barrier repels further diffusion
      - Free electrons in the n region diffuse across the junction and fall into holes p region
      - The junction now become completely depleted and this area is called the Depletion Layer
  - - - the potential across the depletion region in thermal equilibrium
- - - - decreasing built-in junction potential
        
        higher current
      - Forward bias reduce the potential barrier of the diode and establishes the early path for the flow of current
      - IV [CURVE]
        
        Right side or part A graph
        
        Forward bias region
        
        V=0 to Vd
        
        Current exponentially increases with respect to the voltage
        
        V>Vd
        
        Current rapidly increases and only limited by resistance in circuit
        
        Forward bias (process)
        
        Width of depletion region decreasing
        
        Electrons in n-side and holes in p-side gets pushed towards the junction
        
        As applied voltage increases from 0 volts to 0.7 volts (Vd) and the depletion region width reduces from ‘W’ to zero.
        
        Depletion region vanishes at 0.7 volts of applied voltage
        
        Increased diffusion of electrons from n-side to p-side region and holes from p-side to n-side region
        
        Movement of charge carriers (electrons and holes) from region of higher concentration to region of lower concentration
        
        Movement of charge carriers inside pn junction gives rise to current through the circuit
    - - increasing the built in junction potential
        
        lower current
      - potential difference increase the strength of barrier, then prevent the charge carrier to move across the junction. cause the resistivity increase thus no current flow
      - IV [CURVE]
        
        Left side or part B graph
        
        Breakdown region
        
        The rapid increase of the current under reverse bias
        
        Limits the maximum reverse bias voltage that can be applied to p-n diode
        
        AVALANCHE
        
        Involving p-n diode which is moderately doped, thus having thick junction
        
        occurs when high reverse voltage is applied across the diode
        
        occurs at higher reverse voltage than zener breakdown
        
        ZENER
        
        allows current to flow in forward direction and in reverse when the applied reverse voltage is larger than zener voltage
        
        does not damage the diode
        
        p-n diode which is heavily doped on both sides and having thin junction
        
        Reverse bias region
        
        Reverse Saturation Current
        
        V=(-ve) to Voltage breakdown
        
        Very small current flow due to the drift of charge carriers from junction region to terminal region.
        
        Process
        
        Electrons at n-side will get pulled from junction region to the terminal region of n-side
        
        Holes at p-side junction will get pulled towards the terminal region of p-side
        
        Increasing the depletion region width from its initial length, say ‘W’ to some W+x
        
        Increasing the electric field strength and net “diffusion current” is zero
        
        This reverse saturation current is the result of drifting of charge carriers from the junction region to terminal region