If the temperature of a diode increases, then leakage current ____.

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Examoogle · Accepted Answer

Increases

Explanation: The leakage current (also known as reverse saturation current, $I_0$) in a semiconductor diode increases significantly with a rise in temperature. This occurs because thermal energy facilitates the generation of more minority charge carriers, which are the primary contributors to leakage current.

Working Principle: In a p-n junction diode, the reverse saturation current $I_0$ is dependent on the concentration of minority carriers (electrons in p-type, holes in n-type). As temperature increases, the covalent bonds break due to thermal agitation, generating electron-hole pairs throughout the crystal. Since these minority carriers can easily cross the depletion barrier under reverse bias, their increased density leads to a higher reverse leakage current.

Key Formulas: $I_0 \propto T^n e^{-\frac{E_g}{kT}}$ — Dependence of reverse saturation current on temperature; $I_{new} \approx I_{old} \cdot 2^{\frac{\Delta T}{10}}$ — Rule of thumb: leakage current doubles for every 10°C rise in Ge diodes

Key Points: Reverse saturation current is primarily due to thermally generated minority carriers.; For Silicon diodes, the leakage current approximately doubles for every 6°C to 10°C rise in temperature.; Germanium diodes exhibit much higher leakage currents than Silicon diodes at the same temperature.; Excessive leakage current can lead to thermal runaway in high-power applications.

Advantages: Provides a predictable way to monitor thermal stability; Allows usage of diodes as temperature sensors in specific biased modes

Disadvantages: Degrades the rectification efficiency at high temperatures; Increases power dissipation and risk of thermal runaway

Applications: Temperature compensation circuits; Thermal monitoring sensors; High-temperature power electronics design

Additional Info: The exponential dependence on temperature is a fundamental characteristic of semiconductor devices.. Option A is incorrect because leakage current is highly temperature-dependent.. Option B is incorrect because leakage current increases, not decreases, with thermal energy.. Option D is incorrect as leakage current is non-zero even at room temperature.

Answer: C is correct — The leakage current in a diode increases with temperature due to the increased rate of thermally generated minority charge carriers.

Exam Tip: Always remember that while forward resistance decreases with temperature, reverse leakage current increases exponentially, which is the primary reason why Silicon is preferred over Germanium in high-temperature environments.

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