In a p-n junction diode operating under certain reverse bias...

In a p-n junction diode operating under certain reverse bias $V_{r}$, if $V_{r}$ is increased to $3 V_{r}$, what will be the impact on the following parameters?
(a) Depletion width
(b) Contact potential
(c) Junction capacitance
(d) Probability of breakdown

Key Concepts

Junction Capacitance

Junction capacitance arises due to the charge separation in the depletion region and is inversely related to the width of that region. As reverse bias increases, the depletion region widens, leading to a decrease in capacitance, typically following an inverse square root dependency on the applied voltage.

Breakdown Phenomena

Breakdown phenomena, including avalanche and Zener breakdown, occur when the electric field in the depletion region becomes sufficiently high to accelerate carriers to energies that cause impact ionization. Increasing the reverse bias increases the likelihood of these breakdown mechanisms, thereby raising the probability of breakdown at higher voltages.

Contact Potential

The contact potential, or built-in potential, is an intrinsic voltage across the junction due to differences in material properties and doping levels. It generally remains constant regardless of the applied external bias, although the overall potential difference across the junction is affected by the external voltage.

p-n Junction Diode

A p-n junction diode is formed by joining p-type and n-type semiconductors, resulting in a depletion region where mobile charge carriers are depleted. This creates a built-in electric field, which is fundamental to the diode’s rectifying behavior and governs its response to external biases.

Reverse Bias

Reverse bias is the application of a voltage that widens the depletion region by repelling majority carriers. This condition increases the resistance of the junction, reduces the junction capacitance, and elevates the electric field across the depletion region, which can lead to breakdown phenomena under high voltage conditions.

Depletion Region Width

The depletion region width in a semiconductor junction increases with the magnitude of the reverse bias. This relationship is typically proportional to the square root of the applied voltage, meaning that when the reverse bias is increased, the depletion width becomes larger, affecting the device's electrical characteristics.

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