#minority carriers

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

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Doping, Charge Carriers and Conductivity

In an extrinsic semiconductor, the minority carrier concentration is reduced due to:

**Doping** is adding impurity to pure semiconductor to increase carriers, pentavalent (P, As, Sb) donates extra electron, 1 ppm doping in Ge with 4×10²⁸ atoms/m³ gives donor density N_d = 4×10²⁸×10⁻⁶ =4×10²² m⁻³ for 1 ppm, acceptor atoms p-type trivalent B, Al, Ga. Overall charge neutrality maintained because donor ion core positive but electron negative, net neutral. Doping increases majority carriers (electrons in n-type, holes in p-type), enhancing recombination with minority carriers, thus reducing their concentration indirectly. Substituting values gives Increased recombination, which mat

Ref: NCERT > Physics Book > Electronic Devices > Doping, Charge Carriers and Conductivity

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Doping, Charge Carriers and Conductivity

In an n-type semiconductor, the minority carriers are:

**Doping** is adding impurity to pure semiconductor to increase carriers, pentavalent (P, As, Sb) donates extra electron, 1 ppm doping in Ge with 4×10²⁸ atoms/m³ gives donor density N_d = 4×10²⁸×10⁻⁶ =4×10²² m⁻³ for 1 ppm, acceptor atoms p-type trivalent B, Al, Ga. Overall charge neutrality maintained because donor ion core positive but electron negative, net neutral. In an n-type semiconductor, electrons are majority carriers due to pentavalent doping, while holes, generated intrinsically or reduced by recombination, are minority carriers. Substituting values gives Holes, which matches expect

Ref: NCERT > Physics Book > Electronic Devices > Doping, Charge Carriers and Conductivity

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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

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

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