The GATE Grind

GATE 2022 EC – Question 47

Electronic Devices · P-N Junction and Semiconductor Devices · 2 marks · Multiple select

Select the CORRECT statement(s) regarding semiconductor devices.

  1. Electrons and holes are of equal density in an intrinsic semiconductor at equilibrium.
  2. Collector region is generally more heavily doped than Base region in a BJT.
  3. Total current is spatially constant in a two terminal electronic device in dark under steady state condition.
  4. Mobility of electrons always increases with temperature in Silicon beyond 300 K.

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Show answer and explanation

Correct answer: (A) Electrons and holes are of equal density in an intrinsic semiconductor at equilibrium.; (C) Total current is spatially constant in a two terminal electronic device in dark under steady state condition.

Explanation

In an intrinsic semiconductor $n=p=n_i$, so A is true. In a BJT the collector is lightly doped compared with the base (and the emitter most heavily), so B is false. In steady state the total current (conduction plus displacement) must be continuous along a two-terminal device, so C is true. Above 300 K lattice scattering makes electron mobility decrease with temperature, so D is false.