why we do not use intrinsic semiconductor instead of extrinsic semiconductors?

Intrinsic semiconductors, by themselves, have certain limitations that make them less practical for many electronic applications compared to extrinsic (doped) semiconductors. Here are some key reasons why extrinsic semiconductors are preferred:

1. Control of Carrier Concentration: Intrinsic semiconductors have an equal number of electrons and holes (electron-hole pairs) generated at room temperature due to thermal excitation. This means that their carrier concentration (number of charge carriers per unit volume) is relatively low. In electronic devices, precise control over carrier concentration is crucial for controlling device behavior. Extrinsic semiconductors, created by intentional doping with specific impurities, allow engineers to precisely control carrier concentration and tailor the semiconductor's properties for specific applications.

2. Enhanced Conductivity: Intrinsic semiconductors have relatively poor electrical conductivity due to their low carrier concentration. Extrinsic semiconductors, on the other hand, can have significantly higher carrier concentrations, making them more conductive and suitable for carrying electrical currents in devices.

3. Specific Electrical Behavior: Extrinsic semiconductors can be engineered to exhibit specific electrical behaviors. For example, n-type semiconductors are doped with donor impurities, resulting in excess electrons and making them electron-dominant. Conversely, p-type semiconductors are doped with acceptor impurities, creating excess holes and making them hole-dominant. This ability to create n-type and p-type regions is essential for building diodes, transistors, and other semiconductor devices.

4. Device Functionality: Many semiconductor devices, such as diodes, transistors, and integrated circuits, rely on the controlled movement of charge carriers (electrons and holes). Intrinsic semiconductors, with their equal number of electrons and holes, do not offer the same degree of control as extrinsic semiconductors with intentionally introduced carriers. The precise control of carrier concentrations and the ability to create regions with different electrical properties are essential for the functionality of these devices.

5. Improved Performance: Extrinsic semiconductors are engineered for specific performance characteristics, such as higher speed, lower power consumption, and greater efficiency. Doping allows semiconductor manufacturers to optimize the performance of devices and circuits.

In short, while intrinsic semiconductors (e.g. pure silicon) have their place in fundamental semiconductor physics and some specialized applications, they are less practical for most electronic devices. Extrinsic semiconductors (p-type, n-type, pn Junction, diode, transistor etc), achieved through intentional doping, provide the necessary control over carrier concentration and electrical behavior, making them the preferred choice for building a wide range of semiconductor devices that power modern electronics.