PN Junction Diode and its Characteristics

P-N junction diode is the most fundamental and the simplest electronics device. When one side of an intrinsic semiconductor is doped with acceptor i.e, one side is made p-type by doping with n-type material, a p-n junction diode is formed. This is a two terminal device. It appeared in 1950’s.
P-N junction can be step graded or linearly graded. In step graded the concentration of dopants both, in n-side and in p-side are constant up to the junction. But in linearly graded junction, the doping concentration varies almost linearly with the distance from the junction. When the P-N diode is in unbiased condition that is no voltage is applied across it, electrons will defuse through the junction to p-side and holes will defuse through the junction to n-side and they combine with each other.

Thus the acceptor atom near the p-side and donor atom near n-side are left unutilized. An electron field is generated by these uncovered charges. This opposes further diffusion of carriers. So, no movement of region is known as space charge or depletion region.

If, we apply forwards bias to the p-n junction diode. That means if positive side of the battery is connected to the p-side, then the depletion regions width decreases and carriers flow across the junction. If the bias is reversed the depletion width increases and no charge can flow across the junction.

P-N Junction Diode Characteristics

Let's a voltage V is applied across a p-n junction and total current I, flows through the junction. It is given as.
Here, IS = reverse saturation current
e = charge of electron
ɳ = emission co-efficient
KB = Boltzmann constant
T = temperature The current voltage characteristics plot is given below.
The current voltage characteristics. characteristics of p n junc When, V is positive the junction is forward biased and when V is negative, the junction is reversing biased. When V is negative and less than VTH, the current is very small. But when V exceeds VTH, the current suddenly becomes very high. The voltage VTH is known as threshold or cut in voltage. For Silicon diode VTH = 0.6 V. At a reverse voltage corresponding to the point P, there is abrupt increment in reverse current. The PQ portion of the characteristics is known as breakdown region.

P-N Junction Band Diagram

For an n-type semiconductor, the Fermi level EF lies near the conduction band edge. EC but for an p-type semiconductor, EF lies near the valance band edge EV. p n junction band diagram Now, when a p-n junction is built, the Fermi energy EF attains a constant value. In this scenario the p-sides conduction band edge. Similarly n–side valance band edge will be at higher level than Ecn, n-sides conduction band edge of p-side. This energy difference is known as barrier energy. The barrier energy is
band diagram of p-n junctio If we apply forward bias voltage V, across junction then the barrier energy decreases by an amount of eV and if V is reverse bias is applied the barrier energy increases by eV. band of forward biased p n band of reversed biased p n

P-N Junction Diode Equation

The p-n junction diode equation for an ideal diode is given below
Here, IS = reverse saturation current
e = charge of electron
KB = Boltzmann constant
T = temperature
For a normal p-n junction diode, the equation becomes
Here, ɳ = emission co-efficient, which is a number between 1 and 2, which typically increases as the current increases.


Closely Related Articles Vacuum Diode History Working Principle and Types of Vacuum DiodeDiode | Working and Types of DiodeDiode CharacteristicsHalf Wave Diode RectifierFull Wave Diode RectifierDiode Bridge RectifierWhat is Zener Diode?Application of Zener DiodeLED or Light Emitting DiodePIN Photodiode | Avalanche PhotodiodeTunnel Diode and its ApplicationsGUNN DiodeVaractor DiodeLaser DiodeSchottky DiodePower DiodesDiode ResistanceDiode Current EquationIdeal DiodeReverse Recovery Time of DiodeDiode TestingMore Related Articles Amplifier Gain | Decibel or dB GainIntegrated Circuits | Types of ICRegulated Power SupplyLaser | Types and Components of LaserWork FunctionMobility of Charge CarrierWhat are Photo Electrons? Electron volt or eVEnergy Quanta | Development of Quantum Physics Schottky EffectHeisenberg Uncertainty PrincipleSchrodinger Wave Equation and Wave FunctionCyclotron Basic Construction and Working PrincipleSinusoidal Wave SignalCommon Emitter AmplifierRC Coupled AmplifierDifferential AmplifierWave Particle Duality PrincipleSpace ChargeMOSFET | Working Principle of p-channel n-channel MOSFETMOSFET CircuitsMOS Capacitor | MOS Capacitance C V CurveApplications of MOSFETMOSFET as a SwitchMOSFET CharacteristicsPower MOSFETHalf Wave RectifiersFull Wave RectifiersBridge RectifiersClamping CircuitTheory of SemiconductorIntrinsic SemiconductorExtrinsic SemiconductorsEnergy Bands of SiliconDonor and Acceptor Impurities in Semiconductor Conductivity of SemiconductorCurrent Density in Metal and Semiconductor Intrinsic Silicon and Extrinsic SiliconP Type SemiconductorN Type SemiconductorP N Junction Theory Behind P N JunctionForward and Reverse Bias of P N JunctionZener BreakdownAvalanche BreakdownHall Effect Applications of Hall EffectGallium Arsenide SemiconductorSilicon SemiconductorTypes of TransistorsBipolar Junction Transistor or BJTBiasing of Bipolar Junction Transistor or BJTTransistor BiasingTransistor CharacteristicsCurrent Components in a TransistorTransistor Manufacturing TechniquesApplications of Bipolar Junction Transistor or BJT | History of BJTTransistor as a SwitchTransistor as an AmplifierJFET or Junction Field Effect Transistorn-channel JFET and p-channel JFETApplications of Field Effect TransistorDIAC Construction Operation and Applications of DIACTRIAC Construction Operation and Applications of TRIACPhototransistorNew Articles Measurement of Insulation ResistanceAmpere's Circuital LawMechanical Equivalent of HeatTrees and Cotrees of Electric NetworkDifferentiatorIntegrator
electrical engineering app