Q153 / 170 · Manipal (MET) 2019 · Physics

If no external voltage is applied across $p-n$ junction, there would be

  • A
    no electric field across the junction
  • Correct answer
    B
    an electric field pointing from $n$-type to p-type side across the junction
  • C
    an electric field pointing from $p$-type to $n$-type side across the junction
  • D
    a temporary electric field during formation of p-n junction that would subsequently disappear

Solution

Near the junction positive charge is built on $n$-side and negative charge on $P$-side. This sets up potential difference across the junction and internal electric field $E_i$ directed from $n$-side to $P$-side. The equilibrium is established when the field $E_i$ becomes strong enough to stop further diffusion of the majority charge carriers.

Hence, the correct answer is option: 'B'.

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