Question

As shown in the figure, two metal-semiconductor junctions are formed between an n-type semiconductor S and metal M. The work functions of S and M are $\phi_S$ and $\phi_M$, respectively, with $\phi_M > \phi_S$. The I-V characteristics (on linear scale) of the junctions is best represented by 

• A. A
• B. B
• C. C
• D. D

Hint:

For a metal-semiconductor junction with \( \phi_M > \phi_S \), the current increases sharply for a small positive bias voltage due to the Schottky barrier formation.

Answer 1

The Correct Option is A

In this problem, we are given two metal-semiconductor junctions formed between an n-type semiconductor (S) and a metal (M), where the work function of the metal \( \phi_M \) is greater than that of the semiconductor \( \phi_S \). Step 1: Understanding the I-V characteristics. - The I-V curve represents the current (\( I \)) as a function of the voltage (\( V \)) applied to the junction. - For a metal-semiconductor junction, when the metal has a higher work function than the semiconductor, it results in the formation of a Schottky barrier. The current-voltage relationship for such a junction is typically exponential for forward bias and reverse exponential for reverse bias. Step 2: Analyzing the options. - Option (A): The typical I-V characteristic of a Schottky diode shows a sharp rise in current for a small positive voltage, as expected for the case where \( \phi_M > \phi_S \), which corresponds to the forward bias behavior in the figure. This matches the expected behavior, as the current increases rapidly with voltage. - Option (B): This represents an inverted exponential curve, which would be typical for a different configuration of junctions, such as for reverse bias in a Schottky diode or some other types of junctions. - Option (C): This curve represents a moderate exponential rise, which is not typically observed for metal-semiconductor junctions under normal conditions. - Option (D): This curve does not correctly represent the forward bias behavior of a Schottky junction. Thus, the best match for the I-V characteristic of the given metal-semiconductor junction is option (A). Final Answer: (A)