Which parameter of semiconductor diode exhibits positive temperature co-efficient?

Explanation:

Positive Temperature Coefficient of Semiconductor Diode

Definition: A positive temperature coefficient (PTC) refers to the phenomenon where a parameter increases with an increase in temperature. In the context of semiconductor diodes, certain characteristics exhibit a positive temperature coefficient, which can be crucial for their operation and applications.

Correct Option Analysis:

The correct answer is:

Option 1: Reverse Leakage Current

The reverse leakage current of a semiconductor diode exhibits a positive temperature coefficient. This means that as the temperature increases, the reverse leakage current also increases. This behavior is primarily due to the following reasons:

• Thermal Generation: In a semiconductor, increasing temperature leads to an increase in the thermal generation of charge carriers. This results in a higher concentration of minority carriers, which contributes to a larger reverse leakage current.
• Energy Band Gap Reduction: The energy band gap of a semiconductor narrows as the temperature rises. This reduction facilitates easier carrier movement across the junction, further increasing the reverse leakage current.
• Carrier Mobility: While carrier mobility may decrease with increasing temperature, the dominant factor affecting reverse leakage current is the generation of additional charge carriers, which outweighs the impact of reduced mobility.

Implications:

The positive temperature coefficient of reverse leakage current has several implications:

• Thermal Runaway: In high-power applications, excessive reverse leakage current can lead to thermal runaway, where increasing temperature causes further current increase, potentially damaging the diode.
• Device Reliability: Understanding and mitigating the effects of reverse leakage current are essential for ensuring the reliability and longevity of semiconductor devices.
• Design Considerations: Engineers must account for the temperature-dependent behavior of reverse leakage current when designing circuits involving semiconductor diodes.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 2: Reverse Breakdown Voltage

The reverse breakdown voltage of a semiconductor diode generally exhibits a negative temperature coefficient. As temperature increases, the breakdown voltage decreases due to enhanced carrier generation and tunneling effects. This behavior is opposite to what is described by a positive temperature coefficient, making this option incorrect.

Option 3: Forward Voltage

The forward voltage of a semiconductor diode typically decreases with an increase in temperature. This is because higher temperatures reduce the barrier potential of the p-n junction, allowing carriers to move more freely. Hence, the forward voltage exhibits a negative temperature coefficient, not a positive one. Therefore, this option is incorrect.

Option 4: None of the Above

This option is incorrect because, as explained earlier, the reverse leakage current of a semiconductor diode does exhibit a positive temperature coefficient. Selecting "None of the Above" would disregard this established behavior.

Conclusion:

The reverse leakage current of a semiconductor diode is the parameter that exhibits a positive temperature coefficient. This characteristic is crucial for understanding the thermal behavior of diodes and ensuring proper design and application in electronic circuits. Other parameters, such as reverse breakdown voltage and forward voltage, do not exhibit a positive temperature coefficient and instead demonstrate opposite behaviors in response to temperature changes.