Why doping method is used to design a diode circuit​

Because the band gap is so small for semiconductors, doping with small amounts of impurities can dramatically increase the conductivity of the material. Doping, therefore, allows scientists to exploit the properties of sets of elements referred to as “dopants” in order to modulate the conductivity of a semiconductor.

The distance between Earth and Sun is about 0.0000038 times 
the distance to the next nearest star.

(The next nearest star is about 265,300 times as far from us as 
the sun is.) 

The distance between Earth and Sun is about 0.000000000000000000068 
times the distance to the next nearest galaxy.

(The next nearest galaxy is about 14,700,000,000,000,000,000 times 
as far from us as the sun is.) hope this helped.