N-type (negative-type) and P-type (positive-type) semiconductors are two types of semiconductors that play a crucial role in electronic devices. Here are five key differences between N-type and P-type semiconductors:
Dopant Type:
N-type Semiconductor: In an N-type semiconductor, the majority charge carriers are electrons. This is achieved by introducing a small amount of a pentavalent (five valence electrons) impurity, such as phosphorus or arsenic, into the semiconductor crystal lattice. These impurities create extra electrons, leading to an excess of negative charge carriers.
P-type Semiconductor: In a P-type semiconductor, the majority charge carriers are holes, which are vacancies left by electrons. This is achieved by introducing a small amount of a trivalent (three valence electrons) impurity, such as boron or gallium. These impurities create electron vacancies, resulting in an excess of positive charge carriers.
Charge Carriers:
N-type Semiconductor: Electrons are the majority charge carriers in N-type semiconductors.
P-type Semiconductor: Holes (positively charged vacancies left by electrons) are the majority charge carriers in P-type semiconductors.
Conduction Mechanism:
N-type Semiconductor: Conduction in N-type semiconductors occurs primarily due to the movement of electrons.
P-type Semiconductor: Conduction in P-type semiconductors occurs primarily due to the movement of holes.
Electricity Flow:
N-type Semiconductor: Electrons flow from the negative terminal to the positive terminal, constituting conventional current flow.
P-type Semiconductor: Holes flow from the positive terminal to the negative terminal, which is opposite to conventional current flow. In reality, it is the movement of electrons in the direction of the holes that constitutes the current flow.
Band Structure:
N-type Semiconductor: The Fermi level is closer to the conduction band, and electrons are readily available for conduction.
P-type Semiconductor: The Fermi level is closer to the valence band, and holes are readily available for conduction.
Understanding the properties and behaviors of N-type and P-type semiconductors is fundamental in designing and fabricating electronic devices, such as transistors and diodes, which rely on the controlled movement of charge carriers within semiconductor materials.