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#space-charge region

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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

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

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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

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

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