An intrinsic semiconductor has the following properties:

1. Its electron concentration equals its hole concentration.

2. Its carrier density increases with temperature.

3. Its conductivity decreases with temperature.

Question

Question

This question was previously asked in

ESE Electronics 2011 Paper 1: Official Paper

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Answer 1

Explanation:

In intrinsic semiconductor, n_i = n = p

(where n_i = intrinsic concentration, n = e^- concentration and p = hole concentration) so,

Ist property given is true.

Now as J (current density) = σ .E (where σ = conductivity and E =Field in volt).

Where,

σ ∝ T^3/2 where T is temperature.

Now as σ increases with temperature so J also increases with it,

Hence property 2 is true but property 3^rd given is false.

Important Points

Semiconductors are the materials that have a conductivity between conductors (generally metals) and non-conductors or insulators (such as ceramics).
Semiconductors can be compounds such as gallium arsenide or pure elements, such as germanium or silicon.

Extrinsic Semiconductor	Intrinsic semiconductor:
The process of adding impurities to a semiconductor gives rise to an extrinsic semiconductor.	An intrinsic semiconductor is also known as a pure semiconductor in which no other material is intentionally doped. Example: Si, Ge
Extrinsic Semiconductor is of two types: 1. N-type Semiconductor: When impurity added is of pentavalent type. Ex P, As. 2. P-type Semiconductor: When impurity added is of trivalent type. Ex B, In.	In an Intrinsic semiconductor, both holes and electrons have equal concentration equal to the intrinsic concentration.
Doping increases carrier concentration and conductivity.