#reverse bias

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

Ref: NCERT > Physics Book > Electronic Devices > p-n Junction, Depletion Region and Diode Characteristics

View Details

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 Brea

Ref: NCERT > Physics Book > Electronic Devices > p-n Junction, Depletion Region and Diode Characteristics

View Details

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, depleti

Ref: NCERT > Physics Book > Electronic Devices > p-n Junction, Depletion Region and Diode Characteristics

View Details

p-n Junction, Depletion Region and Diode Characteristics

In reverse bias, the width of the depletion region:

**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 reverse bias, the applied voltage increases the barrier height and electric field, widening the depletion region as more immobile charges are exposed due to reduced carrier diffusion. S

Ref: NCERT > Physics Book > Electronic Devices > p-n Junction, Depletion Region and Diode Characteristics

View Details

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

Ref: NCERT > Physics Book > Electronic Devices > p-n Junction, Depletion Region and Diode Characteristics

View Details

PHYSICS

In reverse bias, the width of the depletion region:

In reverse bias, the applied voltage increases the barrier height and electric field, widening the depletion region as more immobile charges are exposed due to reduced carrier diffusion.

Ref: NCERT Physics Textbook for Class XI and XII, Chapter: Electric Charges and Fields and Electrostatic Potential, Topic: Electric field, potential and capacitance concepts.

View Details

PHYSICS

The reverse bias resistance of a p-n junction diode is typically:

In reverse bias, the diode allows only a small reverse saturation current ( μ A ), resulting in a very high resistance compared to the low resistance in forward bias.

Ref: NCERT Physics Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII, continuing as per NCERT advisory for 2026-27), Chapter: Semiconductor Electronics (Latest NCERT 2026-27), Topic: p-n junction diode, reverse bias high resistance, small saturation curren

View Details