#Semiconductors

PHYSICS

A silicon diode has a threshold voltage of approximately:

The threshold or cut-in voltage for a silicon diode is about 0.7 V, beyond which the forward current increases significantly. This follows from latest NCERT 2026-27 principle explaining the concept clearly for NEET students in simple steps as per rationalized syllabus.

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),Topic: Fundamental laws, definitions and applications as per latest NCERT. The section explains governing laws, formulas like μ₀ = 4π.

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PHYSICS

A Ge crystal with 4 × 10²⁸atoms m^{-3 is doped with 1.5 ppm of trivalent impurity. The number of holes per cubic meter i

Given: A Ge crystal with 4 × 10²⁸atoms m^{-3 is doped with 1.5 ppm of trivalent impurity. The number of holes per cubic meter is approximately: Formula: 1.5 ppm = 1.5 × 10⁻⁶. Substitution & Calculation: Number of acceptor atoms = 1.5 × 10⁻⁶ × 4 × 10²⁸= 6 × 10²²m^{-3, each creating one hole, assuming full ionization. Final Result: The computed value matches expected outcome and confirms correct choice as per latest NCERT 2026-27.

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),Topic: Fundamental laws, definitions and applications as per latest NCERT. The section explains governing laws, formulas like μ₀ = 4π.

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PHYSICS

The process of adding impurities to a pure semiconductor is called:

Doping is the deliberate addition of impurities (e.g., pentavalent or trivalent atoms) to a pure semiconductor to increase its conductivity by providing additional charge carriers.

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),Topic: Fundamental laws, definitions and applications as per latest NCERT. The section explains governing laws, formulas like μ₀ = 4π.

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PHYSICS

In an intrinsic semiconductor, the total current is the sum of:

The total current ( I ) in an intrinsic semiconductor is the sum of electron current ( I_e ) and hole current ( I_h ), i.e., I = I_e + I_h . This follows from NCERT principle where relation explains outcome clearly for students.

Ref: NCERT Physics Textbook for Class XI and XII, Chapter: Relevant Physics topic covering fundamental principles,

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PHYSICS

The reverse bias current in a p-n junction diode is mainly due to:

In reverse bias, the current (in μ A ) is due to the drift of minority carriers across the junction, as diffusion is suppressed by the increased barrier height.

Ref: NCERT Physics Textbook for Class XI and XII, Chapter: Current Electricity, Topic: Resistivity, temperature dependence and circuit analysis.

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PHYSICS

In a p-n junction under equilibrium, the net current is:

At equilibrium (no bias), diffusion and drift currents balance each other, resulting in zero net current across the p-n junction. This follows from latest NCERT 2026-27 principle explaining the concept clearly for NEET students in simple steps as per rationalized syllabus.

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: Thermal Properties of Matter (Latest NCERT 2026-27), Topic: Latent heat Q = mL_f, ice melting, L_f = 3.35 × 10⁵ J kg⁻¹ and mass ca

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PHYSICS

The dynamic resistance of a diode is defined as:

Dynamic resistance ( r_d ) is the ratio of a small change in voltage ( Δ V ) to the corresponding small change in current ( Δ I ), i.e., r_d = Δ V / Δ I, reflecting the diode's behavior under small signal variations.

Ref: NCERT Physics Textbook for Class XI and XII, Chapter: Current Electricity, Topic: Resistivity, temperature dependence and circuit analysis.

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PHYSICS

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

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.

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: Thermal Properties of Matter (Latest NCERT 2026-27), Topic: Latent heat Q = mL_f, ice melting, L_f = 3.35 × 10⁵ J kg⁻¹ and mass ca

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PHYSICS

The electric field in the depletion region of a p-n junction is directed from:

The electric field arises from positive ionized donors on the n-side and negative ionized acceptors on the p-side, directed from the n-side (positive) to the p-side (negative).

Ref: NCERT Physics Textbook for Class XI and XII, Chapter: Relevant Physics topic covering fundamental principles,

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PHYSICS

Why does a non-ohmic device, like a diode, exhibit a non-linear current-voltage relationship?

In a diode, resistance depends on the direction and magnitude of the applied voltage due to its semiconductor junction properties. Forward bias reduces resistance, while reverse bias increases it, leading to a non-linear I -versus- V curve.

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),Topic: Fundamental laws, definitions and applications as per latest NCERT. The section explains governing laws, formulas like μ₀ = 4π.

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