A p-n junction is to be created by diffusing boron into an n-type silicon wafer with an existing carrier conc.

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Problem no 15

To create a p-n junction by diffusing boron into an n-type silicon wafer, you need to follow several steps. Here's an explanation of the process:

1. Clean the Silicon Wafer: Start by thoroughly cleaning the silicon wafer to remove any impurities or contaminants. This is typically done using a combination of chemical etching and rinsing steps in a cleanroom environment.

2. Apply Boron Source: Once the wafer is clean, a boron source is applied to the surface. This can be done in various ways, such as using a boron-doped oxide film or depositing a boron-containing compound onto the wafer surface.

3. Diffusion Process: The wafer, along with the boron source, is then subjected to a high-temperature process, typically performed in a furnace or a rapid thermal annealing (RTA) system. The high temperature causes the boron atoms to diffuse into the silicon crystal lattice.

4. Doping Profile: The diffusion process creates a new region in the silicon wafer with an increased concentration of boron atoms. This region is called the p-type region, and it forms the p-n junction with the existing n-type silicon.

5. Annealing: After the diffusion process, the wafer is annealed again to activate the dopant atoms and to repair any crystal lattice damage caused by the diffusion.

6. Contact Formation: Finally, metal contacts are deposited onto the p- and n-type regions of the wafer to allow for external electrical connections.

By following these steps, a p-n junction can be successfully created by diffusing boron into an n-type silicon wafer with an existing carrier concentration.