PN Junctions & Diodes

PN Junctions & Diodes: PN Junction Electrostatics: Built-in Potential, Depletion & Fields, PN Junction Under Bias & the Diode Equation, Junction Capacitance, Switching & Breakdown, Metal–Semiconductor Contacts & Schottky Diodes, Zener, Schottky, TVS & Other Special-Purpose Diodes, Diode Families: Rectifier, Fast-Recovery, PIN, Varactor, Tunnel & TVS, Rectifiers & Capacitor-Input Filters.

• PN Junction Electrostatics: Built-in Potential, Depletion & Fields — What happens when P meets N. Learn junction formation by carrier diffusion, the depletion (space-charge) region of fixed ionised donors and acceptors, the built-in electric field and potential, equilibrium as a balance of drift and diffusion, the equilibrium band diagram, charge, field and potential distributions of the abrupt junction, depletion width and its split between sides, one-sided (p⁺n) junctions, the effect of reverse bias, and linearly graded junctions — with Python computing V_bi, W, x_n, x_p and E_max for several dopings and biases.
• PN Junction Under Bias & the Diode Equation — Deriving the diode equation from physics. Learn how forward bias lowers the barrier and injects minority carriers, the law of the junction (p_n = p_n0·e^(V/V_T)), minority-carrier diffusion into long and short diodes, the Shockley equation I = I_S(e^(V/nV_T) − 1) with I_S expressed through n_i, doping, diffusion lengths and area, reverse leakage (diffusion and depletion-region generation), recombination current and the ideality factor, high-level injection and series resistance, temperature dependence of I_S and of V at constant current (~−2 mV/K), and the family of diode models (ideal, constant-drop, piecewise-linear, exponential, small-signal) — with Python computing I_S from physical parameters, the I–V curve, injected carrier levels and dV/dT.
• Junction Capacitance, Switching & Breakdown — Why a diode is not an ideal switch. Learn depletion (junction) capacitance C_j = εA/W and its reverse-bias dependence, the C–V method for doping profiling, diffusion (storage) capacitance from injected charge, the charge-control model, forward and reverse recovery (storage time t_s, t_rr, Q_rr, soft vs snappy recovery), and breakdown mechanisms — avalanche (impact ionisation) and Zener (band-to-band tunnelling) — their doping and temperature dependence, dynamic resistance, pulse/energy ratings and safe operation — with Python computing C_j(V), C_d, storage time and breakdown voltage vs doping.
• Metal–Semiconductor Contacts & Schottky Diodes — When metal meets semiconductor. Learn work function and electron affinity, the ideal Schottky barrier φ_B = φ_m − χ, Fermi-level pinning by interface states, band diagrams under bias, thermionic emission and the Richardson constant, majority-carrier operation (no stored charge), ideality factor, image-force lowering, reverse leakage and its strong temperature dependence, ohmic contacts by heavy doping and tunnelling (specific contact resistivity), Schottky vs PN diodes, power Schottky, SiC Schottky and RF/mixer Schottky diodes — with Python computing Schottky saturation currents, forward drops vs PN diodes and leakage vs temperature.
• Zener, Schottky, TVS & Other Special-Purpose Diodes — A diode for every job. For each type learn the symbol idea, construction, operation, I–V characteristic, key parameters, advantages, limitations, applications and selection criteria: PN signal and power diodes, fast/ultrafast recovery diodes, Schottky barrier diodes, Zener and avalanche diodes (shunt regulators, references), TVS diodes (surge/ESD clamps), varactors (voltage-tuned capacitance), tunnel diodes (negative resistance), and SiC Schottky — with Python designing a Zener shunt regulator and checking TVS pulse power.
• Diode Families: Rectifier, Fast-Recovery, PIN, Varactor, Tunnel & TVS — The diode zoo and how to choose. For each family — signal/switching, standard rectifier, fast, ultrafast and soft-recovery, high-voltage and high-current diodes, PIN diodes (RF switches, attenuators, photodiodes, power), varactors (abrupt and hyperabrupt, VCOs, PLLs, tuned filters, matching), tunnel diodes (heavy doping, quantum tunnelling, negative differential resistance, oscillators), and TVS/ESD protection diodes (stand-off, breakdown, clamping, peak pulse power, uni/bidirectional, automotive and data lines) — learn structure, operation, I–V, key parameters, applications and selection — with Python computing varactor tuning ranges, PIN RF resistance, tunnel-diode NDR and TVS pulse energy.
• Rectifiers & Capacitor-Input Filters — Turning AC into DC. Learn half-wave, full-wave centre-tapped and bridge rectifiers, peak inverse voltage (PIV), average and RMS output, ripple frequency, efficiency and transformer utilisation, diode drops and losses, the capacitor-input (reservoir) filter and ripple voltage, conduction angle and peak/RMS diode and capacitor currents, surge (inrush) current, LC and π filters, and voltage doublers — with Python designing a bridge rectifier with a reservoir capacitor.