Question

The number of minority carriers crossing the junction of diode depends primarily on the (A) magnitude of potential barrier (B) magnitude of the forward bias barrier. (C) rate of thermal generation of electron hole pair. (D) concentration of doping impurities.

Short answer

The number of minority carriers crossing the junction of a diode primarily depends on the \(rate\) of \(thermal\) generation of electron-hole pairs (Option C). This is because a higher rate of thermal generation leads to a greater number of minority carriers being generated, increasing the number of carriers crossing the junction.

Step-by-step solution

Option A: Magnitude of potential barrier

The potential barrier in a pn-junction diode is the built-in potential difference that opposes the flow of charge carriers across the junction. The magnitude of the potential barrier affects the rate at which minority carriers cross the junction. However, this is not the only factor, and is not the primary factor, as it does not have a direct influence on the number of minority charge carriers generated.

Option B: Magnitude of the forward bias barrier

The forward bias barrier is the applied voltage across the diode terminals, which reduces the potential barrier, allowing charge carriers to cross the junction. The higher the forward bias, the faster minority carriers will cross the junction. However, the magnitude of the forward bias barrier does not directly influence the number of minority carriers generated within the diode.

Option C: Rate of thermal generation of electron-hole pair

This option is the most relevant to the question. Thermal generation of electron-hole pairs leads to the generation of minority carriers. The number of minority carriers in the diode primarily depends on the rate of thermal generation of electron-hole pairs. A higher rate of thermal generation leads to a greater number of minority carriers being generated, increasing the number of carriers crossing the junction.

Option D: Concentration of doping impurities

The concentration of doping impurities affects the overall conductivity of the semiconductor material, and thus affects the number of majority carriers in the material. However, the number of minority carriers is not directly influenced by the doping concentration, and is instead dominated by the thermal generation of electron-hole pairs. Therefore, the most appropriate answer is: (C) rate of thermal generation of electron-hole pair

Key concepts

Minority Carriers

In a pn-junction diode, there are two types of charge carriers: majority and minority carriers. Majority carriers are the dominant charge carriers in a specific region, such as electrons in the n-type and holes in the p-type region. Meanwhile, minority carriers are the less prevalent carriers in each region, such as holes in the n-type and electrons in the p-type region.

The behavior and movement of minority carriers are crucial in the operation of the pn-junction diode. Especially in determining its conductive properties. These minority carriers can move across the diode junction, but their concentration is not as high as the majority carriers.

• Important for understanding current flow in semiconductors.
• Depends significantly on thermal generation of electron-hole pairs.

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