Choose the correct statement(s) from the following:
(A) With increasing reverse bias voltage, the barrier potential across the junction of p-n diode decreases.
(B) A p-type semiconductor can be obtained by doping Si or Ge with trivalent atoms.
(C) A rectifier rectifies dc voltages.
(D) Pure semiconductors are called extrinsic semiconductors.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (B) only
(A) With increasing reverse bias voltage, the barrier potential across the junction of p-n diode decreases. — Incorrect. In reverse bias the applied voltage adds to the barrier, so the effective barrier potential increases (to \( V_0 + V \)) and the depletion layer widens.
(B) A p-type semiconductor can be obtained by doping Si or Ge with trivalent atoms. — Correct. A trivalent atom (B, Al, In) has one electron fewer than needed for four bonds, so it creates a hole; holes become the majority carriers.
(C) A rectifier rectifies dc voltages. — Incorrect. A rectifier converts an ac voltage into a dc voltage; a dc voltage needs no rectifying.
(D) Pure semiconductors are called extrinsic semiconductors. — Incorrect. Pure semiconductors are intrinsic; doped ones are extrinsic.
NCERT (2026-27):
p-n Junction Diode Under Reverse Bias – “… As a result, the barrier height increases and the depletion region widens due to the change in the electric field.”
p-type Semiconductor – “This is obtained when Si or Ge is doped with a trivalent impurity like Al, B, In, etc.”
Application of Junction Diode as a Rectifier – “… So if an alternating voltage is applied across a diode the current flows only in that part of the cycle when the diode is forward biased. This property is used to rectify alternating voltages and the circuit used for this purpose is called a rectifier.”
Summary – “… 5. Pure semiconductors are called ‘intrinsic semiconductors’.”