In MOS A. The substrate fermi potential ϕF is negative in NMOS B. The substrate fermi potential ϕF is positive in NMOS C. The substrate bias voltage VSB is positive in NMOS, negative in PMOS D. The substrate bias voltage VSB is negative in NMOS, positive in PMOS. Choose the correct answer from the options given below:
A & C only
To solve this question, let's examine the statements about the Metal-Oxide-Semiconductor (MOS) structure, specifically concerning NMOS transistors.
- Explanation of Substrate Fermi Potential (φF):
- In semiconductor physics, the Fermi potential (φF) is determined by the doping level of the substrate. For an NMOS (n-channel MOS), the substrate is typically a p-type semiconductor.
- For a p-type substrate, the Fermi level is below the intrinsic Fermi level, meaning that φF is indeed negative. Thus, statement A is correct.
- Explanation of Substrate Bias Voltage (VSB):
- The substrate bias voltage (VSB) is the voltage difference between the source and the substrate. In an NMOS, the source is typically connected to the ground or a lower potential, while the substrate is at a higher potential, resulting in a positive VSB.
- Conversely, in a PMOS (p-channel MOS), the substrate is typically n-type. The source is at a higher potential, and the substrate at a lower potential, making VSB negative.
- Thus, statement C correctly describes the scenario for NMOS and PMOS, making it a correct statement.
- Elimination of Incorrect Options:
- Statement B, which states that the substrate Fermi potential (φF) is positive in NMOS, is incorrect since we established it is negative for a p-type substrate.
- Statement D, which states that VSB is negative in NMOS and positive in PMOS, contradicts the explanation provided in step 2 regarding substrate bias conditions.
Based on the explanations above, the correct answer is: A & C only.
Similar Questions
In enhancement mode MOSFET the saturation (drain) current is given by
(a) \(K\dfrac{W}{L}(V_{gs}-V_{th})^{2}\)
(b) \(K\dfrac{W}{L}(V_{gs}-V_{th})(1+\lambda V_{ds})\)
(c) \(K\dfrac{W}{L}(V_{gs}-V_{th})^{2}(1+\lambda V_{ds})\)
(d) \(K\dfrac{W}{L}(V_{gs}-V_{th})^{2}(1-\lambda V_{ds})\)
Out of these
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