#p-n junction

p-n Junction, Depletion Region and Diode Characteristics

The thickness of the depletion region in a p-n junction is typically:

**p-n junction formation** diffusion of holes from p to n and electrons from n to p leaves ionized donors positive on n-side and acceptors negative on p-side, forming space-charge depletion region with electric field directed from n to p (positive to negative), barrier potential V_b ≈0.3 V Ge, 0.7 V Si, opposes further diffusion, drift current due to minority carriers swept by field balances diffusion at equilibrium net current zero. The depletion region, formed by diffusion and drift, is very thin, on the order of one-tenth of a micrometer ( 0.1 μ m ), due to the sharp transition at the junct

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p-n Junction, Depletion Region and Diode Characteristics

In a p-n junction, the positive space-charge region is located on:

**p-n junction formation** diffusion of holes from p to n and electrons from n to p leaves ionized donors positive on n-side and acceptors negative on p-side, forming space-charge depletion region with electric field directed from n to p (positive to negative), barrier potential V_b ≈0.3 V Ge, 0.7 V Si, opposes further diffusion, drift current due to minority carriers swept by field balances diffusion at equilibrium net current zero. During junction formation, electrons diffuse from n-side to p-side, leaving behind immobile positive ionized donors on the n-side, forming the positive space-char

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p-n Junction, Depletion Region and Diode Characteristics

The current in a forward-biased p-n junction diode is primarily due to:

**Diode characteristics** forward bias reduces barrier, width of depletion region decreases, resistance low ~10-100 Ω, current primarily due to majority diffusion, exponential I = I_s(e^{eV/kT}-1), reverse bias widens depletion region, resistance high ~MΩ, dominant current drift due to minority carriers, reverse saturation current small μA-nA, typically 10⁻⁶ A, increases sharply at breakdown Zener/avalanche. In forward bias, the applied voltage reduces the barrier height, allowing minority carriers to cross the junction and diffuse, resulting in a current (in mA) due to diffusion of holes and

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p-n Junction, Depletion Region and Diode Characteristics

The negative space-charge region in a p-n junction is located on:

**p-n junction formation** diffusion of holes from p to n and electrons from n to p leaves ionized donors positive on n-side and acceptors negative on p-side, forming space-charge depletion region with electric field directed from n to p (positive to negative), barrier potential V_b ≈0.3 V Ge, 0.7 V Si, opposes further diffusion, drift current due to minority carriers swept by field balances diffusion at equilibrium net current zero. Holes diffuse from p-side to n-side, leaving behind immobile negative ionized acceptors on the p-side, forming the negative space-charge region of the depletion l

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p-n Junction, Depletion Region and Diode Characteristics

During p-n junction formation, the depletion region is formed due to:

**p-n junction formation** diffusion of holes from p to n and electrons from n to p leaves ionized donors positive on n-side and acceptors negative on p-side, forming space-charge depletion region with electric field directed from n to p (positive to negative), barrier potential V_b ≈0.3 V Ge, 0.7 V Si, opposes further diffusion, drift current due to minority carriers swept by field balances diffusion at equilibrium net current zero. The depletion region forms due to diffusion of electrons and holes across the junction, leaving behind immobile ionized impurities that create a space-charge regi

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p-n Junction, Depletion Region and Diode Characteristics

The diffusion current in a p-n junction is due to:

**Depletion region** also called space-charge region, thickness typically 0.5 μm, contains no mobile carriers, only fixed ions, negative on p-side, positive on n-side, diffusion current due to concentration gradient, drift current due to field, equilibrium when J_drift + J_diff =0, voltage drop mainly across depletion region. Diffusion current arises from the movement of carriers (holes from p-side to n-side, electrons from n-side to p-side) due to concentration gradients across the junction during its formation. Substituting values gives Concentration gradient, which matches expected behaviou

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p-n Junction, Depletion Region and Diode Characteristics

The space-charge region in a p-n junction is also known as:

**Diode characteristics** forward bias reduces barrier, width of depletion region decreases, resistance low ~10-100 Ω, current primarily due to majority diffusion, exponential I = I_s(e^{eV/kT}-1), reverse bias widens depletion region, resistance high ~MΩ, dominant current drift due to minority carriers, reverse saturation current small μA-nA, typically 10⁻⁶ A, increases sharply at breakdown Zener/avalanche. The space-charge region, formed by immobile ionized impurities after carrier diffusion, is called the depletion region due to the absence of free charge carriers. Substituting values gives

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p-n Junction, Depletion Region and Diode Characteristics

The barrier potential in a p-n junction opposes the flow of:

**Diode characteristics** forward bias reduces barrier, width of depletion region decreases, resistance low ~10-100 Ω, current primarily due to majority diffusion, exponential I = I_s(e^{eV/kT}-1), reverse bias widens depletion region, resistance high ~MΩ, dominant current drift due to minority carriers, reverse saturation current small μA-nA, typically 10⁻⁶ A, increases sharply at breakdown Zener/avalanche. The barrier potential arises due to the space-charge region and opposes the diffusion of majority carriers (electrons from n-side to p-side and holes from p-side to n-side) at equilibrium.

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p-n Junction, Depletion Region and Diode Characteristics

In forward bias, the resistance of a p-n junction diode is:

**Diode characteristics** forward bias reduces barrier, width of depletion region decreases, resistance low ~10-100 Ω, current primarily due to majority diffusion, exponential I = I_s(e^{eV/kT}-1), reverse bias widens depletion region, resistance high ~MΩ, dominant current drift due to minority carriers, reverse saturation current small μA-nA, typically 10⁻⁶ A, increases sharply at breakdown Zener/avalanche. In forward bias, the barrier height decreases, allowing significant current (mA) to flow, resulting in low resistance compared to reverse bias, where resistance is high due to minimal curr

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p-n Junction, Depletion Region and Diode Characteristics

The drift current in a p-n junction is caused by:

**Diode characteristics** forward bias reduces barrier, width of depletion region decreases, resistance low ~10-100 Ω, current primarily due to majority diffusion, exponential I = I_s(e^{eV/kT}-1), reverse bias widens depletion region, resistance high ~MΩ, dominant current drift due to minority carriers, reverse saturation current small μA-nA, typically 10⁻⁶ A, increases sharply at breakdown Zener/avalanche. Drift current results from the electric field in the depletion region, moving electrons from p-side to n-side and holes from n-side to p-side, opposing diffusion at equilibrium. Substituti

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p-n Junction, Depletion Region and Diode Characteristics

The primary function of a p-n junction diode is to:

**Diode characteristics** forward bias reduces barrier, width of depletion region decreases, resistance low ~10-100 Ω, current primarily due to majority diffusion, exponential I = I_s(e^{eV/kT}-1), reverse bias widens depletion region, resistance high ~MΩ, dominant current drift due to minority carriers, reverse saturation current small μA-nA, typically 10⁻⁶ A, increases sharply at breakdown Zener/avalanche. A p-n junction diode allows current in forward bias (low resistance) and blocks it in reverse bias (high resistance), making it ideal for rectification of AC to DC. Substituting values giv

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p-n Junction, Depletion Region and Diode Characteristics

In a reverse-biased p-n junction, the dominant current is due to:

**p-n junction formation** diffusion of holes from p to n and electrons from n to p leaves ionized donors positive on n-side and acceptors negative on p-side, forming space-charge depletion region with electric field directed from n to p (positive to negative), barrier potential V_b ≈0.3 V Ge, 0.7 V Si, opposes further diffusion, drift current due to minority carriers swept by field balances diffusion at equilibrium net current zero. In reverse bias, diffusion is suppressed, and the small current ( μ A ) is due to minority carriers drifting across the junction under the electric field. Substit

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