Understanding Tunnel Diode Characteristics

The question asks to identify the semiconductor device characterized by specific "peak point voltage" and "valley point voltage". These terms are unique identifiers for the behavior of a Tunnel diode.

What are Peak and Valley Point Voltages?

A tunnel diode, also known as an Esaki diode, exhibits a peculiar behavior due to heavy doping, leading to quantum mechanical tunneling. This behavior results in a region of negative differential resistance on its current-voltage (I-V) characteristic curve. This region is defined by two key points:

• Peak Point Voltage ($V_p$): This is the voltage at which the diode reaches its maximum forward current ($I_{peak}$).
• Valley Point Voltage ($V_v$): This is the voltage that follows the peak point, where the current drops to a minimum value ($I_{valley}$) before increasing again with further increases in voltage.

The presence of both a peak and a subsequent valley in the forward bias I-V curve, separated by a region where voltage increases while current decreases (negative differential resistance), is the defining feature of a tunnel diode.

Why Other Diodes Don't Fit

Let's briefly look at why the other options are not the correct answer:

• Zener diode: Zener diodes are known for their breakdown voltage (Zener voltage), which allows them to operate in reverse bias. They do not exhibit a negative differential resistance region with distinct peak and valley points in their forward characteristic.
• Varactor diode: A varactor diode is essentially a voltage-controlled capacitor. Its primary characteristic is the variation of capacitance with applied reverse bias voltage. It doesn't show peak or valley voltages related to current.
• Schottky diode: Schottky diodes are characterized by a metal-semiconductor junction, resulting in a lower forward voltage drop and faster switching speeds compared to standard PN junction diodes. They do not exhibit the negative differential resistance associated with peak and valley point voltages.

Conclusion

Based on the unique current-voltage characteristics, specifically the presence of a negative differential resistance region defined by a peak point voltage and a valley point voltage, the device described is a tunnel diode.