p-n Junction, Depletion Region and Diode Characteristics

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 junction. Substituting values gives

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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-charge region. Substituting values gives N-side, which matches expected behaviour for this semiconductor device

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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 electrons. Substituting values gives Diffusion of charge carriers, which matches expected behaviour for this semiconductor device configuration, confirming doping, depletion and rectifier principles.

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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 layer. Substituting values gives P-side, which matches expected behaviour for this semiconductor

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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 region. Substituting values gives Diffusion of charge carriers, which matches expected behaviour

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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 behaviour for this semiconductor device configuration, confirming doping, depletion and rectifier principles.

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p-n Junction, Depletion Region and Diode Characteristics

A diode in reverse bias primarily allows current 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. In reverse bias, the small current ( μ A ) is due to minority carriers (electrons in p-side, holes in n-side) drifting across the junction under the electric field. Substituting values gives Minority carriers, which matches expected behaviour for this semiconductor device configuration, confirming doping, depletion and rectifier principles.

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p-n Junction, Depletion Region and Diode Characteristics

The reverse current in a diode increases sharply at:

**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 reverse current remains small ( μ A ) until the reverse bias reaches the breakdown voltage ( Vbr ), where it increases sharply due to junction breakdown. Substituting values gives Breakdown voltage, which matches expected behaviour for this semiconductor device configuration, confirming doping, depletion and rectifier principles.

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p-n Junction, Depletion Region and Diode Characteristics

In forward bias, the effective barrier height of a p-n junction 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 applied voltage ( V ) opposes the built-in potential ( V₀ ), reducing the effective barrier height to V₀ - V , allowing more carriers to cross the junction. Substituting values gives V₀ - V, which matches expected behaviour for this semiconductor device configuration, confirming doping, depletion and rectifier principles.

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p-n Junction, Depletion Region and Diode Characteristics

A silicon diode has a threshold voltage of approximately:

**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 threshold or cut-in voltage for a silicon diode is about 0.7 V, beyond which the forward current increases significantly. Substituting values gives 0.7 V, which matches expected behaviour for this semiconductor device configuration, confirming doping, depletion and rectifier principles.

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p-n Junction, Depletion Region and Diode Characteristics

In a reverse-biased p-n junction, the effective barrier height is:

**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. In reverse bias, the applied voltage ( V ) adds to the built-in potential ( V₀ ), increasing the effective barrier height to V₀ + V . Substituting values gives V₀ + V, which matches expected behaviour for this semiconductor device configuration, confirming doping, depletion and rectifier principles.

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p-n Junction, Depletion Region and Diode Characteristics

The forward current in a p-n junction diode increases significantly beyond:

**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 forward current rises exponentially after the applied voltage exceeds the threshold (cut-in) voltage, reducing the barrier height significantly. Substituting values gives Threshold voltage, which matches expected behaviour for this semiconductor device configuration, confirming doping, depletion and rectifier principles.

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