To solve this problem, we need to understand the concept of sheet resistance in semiconductors. The sheet resistance (\(R_s\)) is a measure of resistance of thin films that are nominally uniform in thickness. It is used for various thin films, including metal and semiconductors.

The formula for sheet resistance is given by:

\(R_s = \frac{\rho}{t}\)

Where:

• \(\rho\) is the resistivity of the material.
• \(t\) is the thickness of the material.

This relation indicates that sheet resistance is directly proportional to the resistivity and inversely proportional to the thickness of the semiconductor layer. Therefore, option (a) \(\frac{\rho}{t}\) is correct.

Now, let's consider option (c), which states:

\(R_s = \frac{R}{t}\)

Where:

• \(R\) is the resistance of the entire semiconductor layer.
• \(t\) is the thickness.

This option is equivalent to the concept of sheet resistance by considering \(R\) as the product of resistivity and geometry dimensions (length/area).

Option (b) \(\frac{\rho L}{t A}\) can be seen as a transformation of resistivity to sheet resistance by taking into account the area (\(A\)) and length (\(L\)) representing the full volume resistivity formula \(R = \frac{\rho L}{A}\).

Thus, options (b) and (c) are conceptually correct when referring to sheet resistance. Hence, the correct answer is (b) and (c) are correct.