The electric field V_0 in the depletion region reinforces the drift current I_S, unlike diffusion current.
A covalent bond is a stable balance of attractive and repulsive forces between atoms when they share electrons.
A negative voltage VR is applied, resulting in a voltage differential across the depletion zone of V0 + VR, and ID < IS.
It pushes majority carriers (holes in the p-region and electrons in the n-region) toward the junction and reduces the width of the depletion zone.
The current component attributed to the flow of holes is given by the equation I = Aqpv, where I is the current, A is the cross-sectional area, q is the magnitude of the electron charge, p is the concentration of holes, and v is the drift velocity of holes.
A p-type semiconductor is created by doping silicon with an element that has a valence of 3, such as boron, to increase the concentration of holes (p).
Silicon is the best and most widely used semiconductor.
A voltage equal to the barrier potential, with the proper polarity, must be applied across a P-N junction before electrons will begin to flow.
No, removing the barrier voltage does not facilitate diffusion; it only removes the electromotive force that opposes it.
p-type semiconductor
A silicon atom has four valence electrons and requires four more to complete its outermost shell.
The diffusion current moves in the same direction as the movement of holes and opposite to that of electrons.
A dc voltage VR is applied.
When an electron is freed, it leaves behind a hole, which is an empty spot with a positive charge.
The resistance of the material will be low and current will flow freely.
There will be fewer free electrons, resulting in high resistance and less current flow.
Doping intrinsic semiconductors is the intentional introduction of impurities into an extremely pure (intrinsic) semiconductor for the purpose of changing carrier concentrations.
The diffusion current is maintained by a constant flow of both free electrons and holes towards the junction, despite low diffusion lengths and recombination.
At the instant of the P-N junction formation, free electrons near the junction in the n region begin to diffuse across the junction into the p region where they combine with holes.
A valence electron is an electron that participates in the formation of chemical bonds.
Boron
The barrier potential is the electric field created in the depletion region due to positive and negative charges on opposite sides of the junction, which acts as a barrier to free electrons in the n region.
Insulators have high resistance which suppresses electrical current flow.
Thermal generation at room temperature breaks covalent bonds, producing free electrons and holes for current conduction.
In the open-circuit condition, minority carriers are evenly distributed throughout the non-depletion regions, defined as either np0 or pn0.
Under open-circuit conditions, no net current flow exists within the pn-junction.
The externally applied voltage V_F subtracts from the barrier voltage V_0, decreasing the effective barrier.
A barrier voltage V0 exists, with no voltage applied and ID = IS.
At the pn junction with no applied voltage, free electrons and holes closest to the junction recombine and eliminate one another.
The smaller circles represent minority carriers, not bound charges.
A PN junction is defined as an interface between two types of semiconductor materials (p-type and n-type semiconductors) inside a single crystal of semiconductor.
At low temperatures, all covalent bonds in silicon are intact, resulting in zero conductivity.
The depletion region is filled with 'uncovered' bound charges that have lost their majority carriers.
The drift velocity increases with increasing electric field, contributing to the mobility of the carriers.
The three conditions are open-circuit, reverse bias, and forward bias.
Carrier diffusion is the flow of charge carriers from an area of high concentration to an area of low concentration, requiring a non-uniform distribution of carriers.
The built-in voltage (V0) is applied across the depletion region, not the terminals of the pn-junction.
n-type semiconductor
The electric field in the depletion region acts as a barrier to free electrons, requiring external energy to move electrons across it.
Copper, silver, gold, aluminum, and nickel are the best element conductors.
Yes, alloys like brass and steel are also good conductors.
No, the drift current I_S is unaffected by reverse bias but is dependent on temperature.
The heavier the doping, the greater the conductivity or the lower the resistance.
Bound charges are attracted by free electrons and holes in the p-type and n-type semiconductors, respectively, and remain weakly 'bound' to these majority carriers without recombining.
It introduces an extra electron into the lattice compared to the silicon atom.
A steady-state gradient is reached.
Diffusion current is caused by the movement due to variation in the carrier concentration.
The depletion zone becomes thin enough such that the barrier voltage (V0 – VF) cannot stop the diffusion current.
Virtually any resistance can be achieved.
At room temperature, some covalent bonds break due to thermal energy, freeing electrons and creating holes, which increases conductivity to greater than zero.
The flow occurs due to the concentration gradient created by the injected holes.
The pn junction appears with open-circuited terminals.
The concentration of minority charge carriers increases on either side of the junction until a steady-state gradient is reached.
Positive carriers (holes) move in the same direction as the electric field.
When equilibrium is reached, the magnitudes of diffusion and drift currents equal one another, resulting in no net current flow.
Phosphorus
The outer valence electrons of silicon are tightly bound together with one another, making them difficult to dislodge for current flow.
I_D will fall to 0 A.
A P-type semiconductor material has a shortage of electrons with vacancies called holes.
Both the free electron and the hole contribute to conduction by moving about the crystal lattice.
Diffusion begins when free electrons and holes closest to the junction start to recombine.
Diffusion current is defined as the current flow density attributed to the movement of charge carriers, such as holes and electrons, driven by concentration gradients. For holes, it is given by Jp = -qDp (dp/dx), and for electrons, it is Jn = -qDn (dn/dx), where D is the diffusion constant.
A valence electron is the single electron in the outer shell of good conductors that can be easily stripped from the atom, allowing for current flow.
The positive ('p') side contains an excess of holes.
Doping
At low temperatures, all covalent bonds in silicon are intact, resulting in zero conductivity.
As the magnitude of V0 increases, the magnitude of the diffusion current (ID) decreases.
Atoms with one or two valence electrons more than a closed shell are highly reactive because the extra electrons are easily removed to form positive ions.
Free electrons may wander from their parent atom, while holes attract neighboring electrons, facilitating current flow.
Repulsive forces will drive the diffusion of carriers, leading to a change in concentrations and eventually a uniform distribution.
A dc voltage VF is applied.
The net current flow is given by Inet = ID – IS, where ID is the diffusion current and IS is the drift current.
It reduces the rate of diffusion, which in turn reduces the diffusion current I_D.
An N-type semiconductor material has extra electrons.
The overall current density is the sum of the drift and diffusion currents.
A positive voltage VF is applied, leading to a voltage differential across the depletion zone of V0 - VF, and ID > IS.
They form a pn junction with no applied voltage, where the n-type semiconductor is filled with free electrons and the p-type semiconductor is filled with holes.
Silicon crystal structure described previously is not sufficiently conductive at room temperature. Additionally, a dependence on temperature is not desirable.
Uncovered bound charges create a voltage differential across the depletion region, and the magnitude of this barrier voltage (V0) increases as diffusion continues.
Drift current is caused by the movement due to electric fields.
Most insulators are compounds of several elements with tightly bound atoms, making it difficult for electrons to flow.
The depletion region begins to form as diffusion occurs and free electrons recombine with holes.
To generate and control the flow of an electrical current.
Drift current arises from the movement of carriers in response to an applied electric field.
Diffusion current is generated by the movement of charge carriers from higher concentration to lower concentration, occurring when a semiconductor is doped non-uniformly.
The rate of majority carriers crossing the junction equals that of recombination.
Good insulating semiconductor material, such as pure silicon, is referred to as intrinsic.
External energy must be applied to move electrons across the barrier of the electric field in the depletion region.
Yes, salt water is an example of a good liquid conductor.
It increases the rate of diffusion, which increases the diffusion current I_D.
The p-side or positive side of the semiconductor has an excess of holes.
Initially, a small forward-bias voltage (V_F) is applied, which pushes majority carriers (holes in the p-region and electrons in the n-region) toward the junction and reduces the width of the depletion zone. This force is opposed by the built-in voltage V_0.
Semiconductors are materials that can be conditioned to act as good conductors, good insulators, or anything in between.
Common elements such as carbon, silicon, and germanium are semiconductors.
The formula for hole diffusion current density is Jp = -qDp (dp/dx), where Jp is the hole diffusion current density, q is the charge of the hole, Dp is the diffusion constant for holes, and dp/dx is the gradient of hole concentration.
An n-type semiconductor is created by doping silicon with an element that has a valence of 5, such as phosphorus, which is a donor, to increase the concentration of free electrons (n).
There is no voltage differential outside of the depletion region due to the neutralizing effect of positive and negative bound charges.
The components involved are the flow of holes, the flow of electrons, and the flow of diffusion current (ID).
The built-in voltage (V0) is the equilibrium value of barrier voltage, generally between 0.6 and 0.9 V for silicon at room temperature.
Conductors have low resistance which allows electrical current flow.
Yes, pure semiconductor materials like silicon can act as excellent insulators due to their crystal lattice structure, where atoms are tightly bound and electrons are not free for current flow.
No, power cannot be drawn from the built-in voltage (V0).
Negative carriers (electrons) move in the opposite direction to the electric field.
It illustrates the inner core of silicon atoms and how covalent bonds are formed by sharing valence electrons.
Semiconductor material is often used as an insulator.
The pn junction will conduct significant current I_D.
The n-side or negative side of the semiconductor has an excess of electrons.
A hole is an empty spot with a positive charge left by a freed electron in the crystal lattice, and it is free to move about.
The concentration of minority charge carriers increases on either side of the junction until a steady-state gradient is reached.
Insulators have a high resistance, preventing current from flowing through them.
The barrier potential is the potential difference of the electric field across the depletion region, required to move electrons through the electric field, approximately 0.7V for silicon.
The drift current attributed to holes increases with the electric field and is influenced by charge carrier concentration, following Ohm's law.
The formula for electron diffusion current density is Jn = -qDn (dn/dx), where Jn is the electron diffusion current density, q is the charge of the electron, Dn is the diffusion constant for electrons, and dn/dx is the gradient of free electron concentration.
The barrier voltage (V0) is an electric field whose polarity opposes the direction of diffusion current (ID).
Thermal energy causes some covalent bonds to break, freeing electrons and creating holes, which facilitates current flow.
At room temperature, sufficient thermal energy breaks some covalent bonds, freeing an electron and creating a hole.
The drift current I_S is a component of current due to minority carrier drift, which occurs when thermally generated holes in p-type and n-type materials move toward the edge of the depletion region and are swept across it by the electric field V_0.
A covalent bond is a form of chemical bond in which two atoms share a pair of electrons.
A concentration gradient, created by non-uniform distribution of carriers, leads to the generation of diffusion current.
Semiconductors can allow or suppress electrical current flow.
The externally applied voltage V_R adds to the barrier voltage V_0, increasing the effective barrier.
The commonly used semiconductor material is silicon.
By controlling the doping of silicon, the semiconductor material can be made as conductive as desired.
A semiconductor element has four electrons in its outer or valence orbit.
Boron has three electrons in the valence band and tries to bond to four silicon atoms, leading to the appearance of holes as it attempts to form four covalent bonds.
Good conductors usually have only one electron in their outer shell, known as a valence electron, which is easily stripped from the atom to produce current flow.
Good insulators include glass, ceramic, plastics, and wood.
The depletion region is a region in a P-N junction diode where no mobile charge carriers are present.
A concentration profile arises due to the continuous injection of holes.
The negative ('n') side contains an excess of electrons in the outer shells of atoms within the semiconductor.
The drift current is mainly influenced by the external electric field and charge carrier concentration.
A barrier voltage V0 exists.
Silicon atoms form a lattice structure by sharing pairs of valence electrons, which creates covalent bonds.
Good conductors have low resistance, allowing electrons to flow through them with ease.
At 0K, all bonds in silicon are intact, and no free electrons are available for current conduction.
Minority carriers, such as thermally generated holes, contribute to the drift current I_S by moving toward the depletion region and being swept across it by the electric field.
Silicon in its pure form is considered a great insulator.
Semiconductor materials can be doped with other atoms to add or subtract electrons.
Drift and diffusion are responsible for generating current in semiconductors.
The net motion of charged particles generates a drift current that is in the same direction as the applied electric field.
In its pure state, semiconductor material is an excellent insulator.
Minimal current flows in the reverse bias case.
The P-N junction consists of a p-type semiconductor, an n-type semiconductor, and a metal contact for connection.
