Intrinsic and extrinsic semiconductors refer to semiconductor materials with different properties and behaviors. Here are five key differences between intrinsic and extrinsic semiconductors:
Impurity Content:
Intrinsic Semiconductor: Intrinsic semiconductors are pure semiconducting materials without intentional impurities. They consist of elements from group IV of the periodic table, such as silicon (Si) or germanium (Ge). Intrinsic semiconductors have an equal number of electrons and holes, and their electrical conductivity is influenced by temperature.
Extrinsic Semiconductor: Extrinsic semiconductors are doped with specific impurities to enhance their electrical properties. Dopants, which are elements from group III or V of the periodic table, introduce extra charge carriers into the semiconductor crystal lattice. This intentional doping significantly modifies the conductivity of the material.
Carrier Concentration:
Intrinsic Semiconductor: In intrinsic semiconductors, the concentration of electrons (negative charge carriers) and holes (positive charge carriers) is equal. The number of charge carriers is primarily determined by temperature and the energy required to create electron-hole pairs.
Extrinsic Semiconductor: Extrinsic semiconductors have a higher concentration of charge carriers due to intentional doping. Doping introduces either extra electrons (n-type doping) or holes (p-type doping), significantly influencing the conductivity and other electrical properties.
Conductivity Type:
Intrinsic Semiconductor: Intrinsic semiconductors are neither n-type nor p-type; they have equal concentrations of electrons and holes, making them non-conductive at absolute zero temperature.
Extrinsic Semiconductor: Extrinsic semiconductors can be either n-type or p-type, depending on the type of dopant used. N-type semiconductors have an excess of electrons, while p-type semiconductors have an excess of holes.
Conduction Mechanism:
Intrinsic Semiconductor: Conduction in intrinsic semiconductors primarily occurs due to the thermal generation of electron-hole pairs. Electrons gain energy from the thermal environment, breaking free from their bonds and creating holes in the crystal lattice.
Extrinsic Semiconductor: Conduction in extrinsic semiconductors is influenced by both thermally generated carriers and the carriers introduced by intentional doping. The dopants create majority carriers, significantly affecting the conductivity.
Applications:
Intrinsic Semiconductor: Intrinsic semiconductors are less commonly used in practical electronic applications due to their limited conductivity at room temperature. However, they serve as a foundation for understanding semiconductor physics.
Extrinsic Semiconductor: Extrinsic semiconductors are extensively used in electronic devices. The ability to control and manipulate the concentration and types of charge carriers through doping makes extrinsic semiconductors the basis for various semiconductor devices, including transistors and diodes.
Understanding the differences between intrinsic and extrinsic semiconductors is crucial for semiconductor physics and the design and development of electronic devices. The intentional introduction of impurities allows engineers to tailor the electrical properties of semiconductors to meet specific application requirements.