Question

The region which is least doped in a transistor will be:

Answer 1

The minus'-' sign indicates it's dopedvery very less compared to the emitter and collector. The middle region is called the Base, and it's this regionthat serves as a gate, regulating flow of charge from Emitter to collector. The doping of base is just one tenth of that of collector.

Answer 2

Least doped region of transistor:

• The base region is less doped as a result of those maximum current streams from the emitter to the collector, through the base.  
• Less doping in base region lets less recombination of charges while moving from emitter to the base, therefore maximum charge carriers move towards the collector allowing Ic to be maximum.
• While the emitter region is a highly doped region of the transistor

Hope it helped...