Why in case of a transistor , the emitter is heavily doped ?

In a transistor,

A transistor has

In a transistor, the emitter current is

Among emitter base and collector regions of a a transistor which one is the most heavily doped.

The part of a transistor, which is heavily doped to produce a large number of majority carriers is called:

Why is the base of a transistor made thin and is lightly doped?

In an n-p-n transistor, the emitter current is

What kinds of biasing are required to the collector and base of a transistor in a common emitter amplifier?

The current gain of a transistor is defined as

When is a transistor said to be in active state ?