Semiconductor · Physics · Class 12

A pure Si crystal having $5 \times 10^{28}$ atoms $\mathrm{m}^{-3}$ is dopped with 1 ppm concentration of antimony. If the concentration of holes in the doped crystal is found to be $4.5 \times 10^9 \mathrm{~m}^{-3}$, the concentration (in $\mathrm{m}^{-3}$ ) of intrinsic charge carriers in Si crystal is about

During the formation of a $$p$$-$$n$$ junction:

Assertion (A) : The resistance of an intrinsic semiconductor decreases with increase in its temperature.

Reason (R) : The number of conduction electrons as well as hole increase in an intrinsic semiconductor with rise in its temperature.

In an extrinsic semiconductor, the number density of holes is $$4 \times 10^{20} \mathrm{~m}^{-3}$$. If the number density of intrinsic carriers is $$1.2 \times 10^{15} \mathbf{m}^3$$, the number density of electrons in it is

Pieces of copper and of silicon are initially at room temperature. Both are heated to temperature T. The conductivity of

The formation of depletion region in a $$p$$-$$n$$ junction diode is due to

(a) Explain the characteristics of a $p-n$ junction diode that makes it suitable for its use as a rectifier.

(b) With the help of a circuit diagram, explain the working of a full wave rectifier.

Explain the following, giving reasons:

(a) A doped semiconductor is electrically neutral.

(b) In a $p$ - $n$ junction under equilibrium, there is no net current.

(c) In a diode, the reverse current is practically not dependent on the applied voltage.

(a) Draw the circuit arrangement for studying V-I characteristics of a $$p$$-$$n$$ junction diode in (i) forward biasing and (ii) reverse biasing. Draw the typical V-I characteristics of a silicon diode. Describe briefly the following terms: (i) minority carrier injection in forward biasing and (ii) breakdown voltage in reverse biasing.

OR

(b) Name two important processes involved in the formation of a p-n junction diode. With the help of a circuit diagram, explain the working of junction diode as a full wave rectifier. Draw its input and output waveforms. State the characteristic property of a junction diode that makes it suitable for rectification.

Draw energy band diagram for an $$n$$-type and $$p$$-type semiconductor at $$\mathrm{T}>0 \mathrm{~K}$$.

Answer the following giving reasons:

(i) A $$p$$-$$n$$ junction diode is damaged by a strong current.

(ii) Impurities are added in intrinsic semiconductors.