Semiconductors:
Semiconductors are materials with electrical conductivity between that of conductors and insulators. Their conductivity can be modified by adding impurities (doping) to create two types: P-type and N-type semiconductors.
Majority Charge Carriers: 
N-type Semiconductor:
Formed by doping a pure semiconductor (like Silicon or Germanium) with Pentavalent impurities (atoms with 5 valence electrons), such as Phosphorus (P), Arsenic (As), or Antimony (Sb).
Pentavalent impurities are called Donor impurities because they donate extra electrons.
Four of the five valence electrons form covalent bonds with neighboring silicon atoms, while the fifth electron becomes a free electron that can move freely.
Since electrons are negatively charged and are the majority carriers, this type is called N-type (Negative-type).
Majority carriers: Electrons
Minority carriers: Holes
P-type Semiconductor:
Formed by doping a pure semiconductor with Trivalent impurities (atoms with 3 valence electrons), such as Boron (B), Aluminum (Al), or Gallium (Ga).
Trivalent impurities are called Acceptor impurities because they create "holes" that can accept electrons.
With only three valence electrons, they cannot complete all four covalent bonds with neighboring silicon atoms, creating a hole (absence of electron) in the crystal structure.
These holes act as positive charge carriers and can move through the crystal when electrons jump into them.
Since holes are positively charged and are the majority carriers, this type is called P-type (Positive-type).
Majority carriers: Holes
Minority carriers: Electrons
Visual Representation:
N-type Semiconductor: 


Applications:
Both N-type and P-type semiconductors are used together to form PN junction diodes, transistors, solar cells, LEDs, and various other electronic components.
The junction between P-type and N-type materials creates a depletion region that is fundamental to modern electronics.
Final Answer: \[ \boxed{\text{P-type: Holes (majority carriers), \quad N-type: Electrons (majority carriers)}} \]
Assuming in forward bias condition there is a voltage drop of \(0.7\) V across a silicon diode, the current through diode \(D_1\) in the circuit shown is ________ mA. (Assume all diodes in the given circuit are identical) 

