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In semiconductor physics, the depletion region, also called depletion layer or depletion zone, as well as the junction region or the space charge region is an insulating region within a conductive, doped semiconductor material where the charge carriers have diffused away or have been swept away by an electric field. A semiconductor is a material that is an insulator at very low temperature, but which has a sizable electrical conductivity at room temperature. ...
In semiconductor production, doping refers to the process of intentionally introducing impurities into an intrinsic semiconductor in order to change its electrical properties. ...
A semiconductor is a solid whose electrical conductivity is in between that of a conductor and that of an insulator, and can be controlled over a wide range, either permanently or dynamically. ...
Charge carrier denotes in physics a free (mobile, unbound) particle carrying an electric charge. ...
diffusion (disambiguation). ...
In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ...
The depletion region is so named because it is formed from a conducting region by removal of all free charge carriers, leaving none to carry a current. Understanding the depletion region is key to explaining modern semiconductor electronics: the operation of diodes, bipolar junction transistors, field-effect transistors, and variable capacitance diodes rely on depletion region phenomena. A semiconductor is a solid whose electrical conductivity is in between that of a conductor and that of an insulator, and can be controlled over a wide range, either permanently or dynamically. ...
This article is about the engineering discipline. ...
Closeup of the image below, showing the square shaped semiconductor crystal various semiconductor diodes, below a bridge rectifier Structure of a vacuum tube diode In electronics, a diode is a two-terminal component, almost always one that has electrical properties which vary depending on the direction of flow of charge...
A bipolar junction transistor (BJT) is a type of transistor. ...
Large power N-channel field effect transistor The field-effect transistor (FET) is a type of transistor that relies on an electric field to control the shape and hence the conductivity of a channel in a semiconductor material. ...
Varicap schematic symbol A varicap diode, varactor diode or tuning diode is a type of diode used in electronic circuits. ...
The following discussion is limited to the pn junction and the MOS capacitor, but depletion regions arise in all the devices mentioned above. Categories: Possible copyright violations ...
The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is by far the most common field-effect transistor in both digital and analog circuits. ...
Formation of depletion region in a pn junction
 Top: pn junction before diffusion; Bottom: After equilibrium is reached
 Top: hole and electron concentrations through the junction; Second from top: charge densities; Third: electric field; Bottom: electric potential A depletion region forms spontaneously across a P-N junction, and is most easily described when the junction is in thermal equilibrium or. more specifically, in dynamic equilibrium.[1] , [2] Electrons and holes will diffuse into regions with lower concentrations of electrons and holes, much as ink will diffuse into water until it is uniformly distributed throughout. N-type semiconductor has an excess of free electrons compared to the P-type region, and P-type has an excess of holes compared to the N-type region. Therefore when N-doped and P-doped pieces of semiconductor are placed together to form a junction, electrons will diffuse into the P-side and holes will diffuse into the N-side. Departure of an electron on the N-side for the P-side leaves a positive donor ion behind on the N-side, and likewise the hole leaves a negative acceptor ion on the P-side. Following transfer, the injected electrons come into contact with holes on the P-side and are eliminated by recombination. Likewise for the injected holes on the N-side. The net result is the injected electrons and holes are gone, leaving behind the charged ions adjacent to the interface in a region with no mobile carriers (the depletion region). The exposed ions are positive on the N side and negative on the P side, creating an electric field that counteracts the continued diffusion of charge carriers. When the electric field is sufficient to arrest further transfer of holes and electrons, the depletion region reaches its equilibrium dimensions. Integrating the electric field across the depletion region determines what is called the built-in voltage (also called the junction voltage or barrier voltage or contact potential). Image File history File links Pn_Junction_Diffusion_and_Drift. ...
Image File history File links Pn_Junction_Diffusion_and_Drift. ...
Image File history File links Size of this preview: 576 × 599 pixelsFull resolution (1233 × 1283 pixel, file size: 116 KB, MIME type: image/png) A PN junction in thermal equilibrium with zero bias voltage applied. ...
Image File history File links Size of this preview: 576 × 599 pixelsFull resolution (1233 × 1283 pixel, file size: 116 KB, MIME type: image/png) A PN junction in thermal equilibrium with zero bias voltage applied. ...
A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ...
A dynamic equilibrium occurs when two reversible processes occur at the same rate. ...
For other uses, see Electron (disambiguation). ...
For the following two reasons the electron hole was introduced into calculations: If an electron is excited into higher state it leaves a hole in its old state. ...
In semiconductor production, doping refers to the process of intentionally introducing impurities into an intrinsic semiconductor in order to change its electrical properties. ...
In semiconductor production, doping refers to the process of intentionally introducing impurities into an intrinsic semiconductor in order to change its electrical properties. ...
In solid state physics, recombination is the process by which the broken semiconductor crystal bonds are restored, via a mutual elimination of an electron and a hole, the complementary charge carriers. ...
Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ...
This article is about the electrically charged particle. ...
In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ...
In the late-18th century, scientists developed sensitive instruments for detecting electrification, otherwise known as electrostatic charge imbalance. ...
- Conduction in semiconductor devices is a combination of charge driven by electric field (drift) and by diffusion. The current density is then
-
-
- j = σ E - D ∇qp
- with q the elementary charge and p the hole density. Diffusion moves the carriers in the direction of decreasing concentration, so for holes a negative current results for a positive density gradient. (If the carriers are electrons, replace hole density p by the negative of the electron density n). When the two current components balance, as in the pn-junction depletion region at dynamic equilibrium, the current is zero due to the Einstein relation, which relates D to σ.
Under reverse bias (P negative with respect to N), the potential drop across the depletion region increases, widening the depletion region and increasing the drift component of current while decreasing the diffusion component. Carrier density is small and only a very small reverse saturation current flows. Forward bias (P positive with respect to N) narrows the depletion region and lowers the barrier to carrier injection. Diffusion component of current greatly increases and drift component decreases. Carrier density is large (exponential), making the junction conductive and allowing a large forward current.[3] The mathematical description of the current is provided by the Shockley diode equation. The low current conducted under reverse bias and large current under forward bias is an example of rectification. In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ...
Not to be confused with electrical conductance, a measure of an objects or circuits ability to conduct an electric current between two points, which is dependent on the electrical conductivity and the geometric dimensions of the conducting object. ...
In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ...
Ficks laws of diffusion describe diffusion, and define the diffusion coefficient D. // History Ficks laws of diffusion were derived by Adolf Fick in the year 1855. ...
For other uses, see Gradient (disambiguation). ...
Charge density is the amount of electric charge per unit volume. ...
The elementary charge (symbol e or sometimes q) is the electric charge carried by a single proton, or equivalently, the negative of the electric charge carried by a single electron. ...
For the following two reasons the electron hole was introduced into calculations: If an electron is excited into higher state it leaves a hole in its old state. ...
A dynamic equilibrium occurs when two reversible processes occur at the same rate. ...
In physics, in kinetic theory the Einstein relation is a previously unexpected connection revealed by Einstein in his 1905 paper on Brownian motion: linking D, the Diffusion constant, and μ, the mobility of the particles; where k is Boltzmanns constant, and T is the absolute temperature. ...
A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ...
Closeup of the image below, showing the square shaped semiconductor crystal various semiconductor diodes, below a bridge rectifier Structure of a vacuum tube diode In electronics, a diode is a two-terminal component, almost always one that has electrical properties which vary depending on the direction of flow of charge...
AC, half-wave and full wave rectified signals A rectifier is an electrical device, comprising one or more semiconductive devices (such as diodes) or vacuum tubes arranged for converting alternating current to direct current. ...
 Metal–oxide–semiconductor structure Image File history File links Mos_capacitance. ...
Image File history File links Mos_capacitance. ...
Formation of depletion region in an MOS capacitor Another example is the MOS capacitor shown in the figure at right. The figure shows a P-type substrate. Initially, suppose the semiconductor is charge neutral, with the charge due to holes exactly balanced by the negative charge due to acceptor doping impurities. If now a positive voltage is applied to the gate, which is done by introducing positive charge on the gate, some positively charged holes in the semiconductor region nearest the gate are repelled by the positive charge on the gate, and leave the device through the bottom contact. When these holes leave, they leave behind a depleted region that is insulating because no mobile holes are left there, only the immobile, negatively charged acceptor impurities. The more positive charge that is placed upon the gate, the more positive the applied gate voltage becomes, and the more holes must leave the semiconductor surface, making the depletion region wider. (In this device there is a limit to how wide the depletion width may become that is set by the onset of an inversion layer of carriers in a thin layer or channel near the surface. The above discussion applies for voltages low enough that an inversion layer does not form.) The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is by far the most common field-effect transistor in both digital and analog circuits. ...
An extrinsic semiconductor is a semiconductor that has been introduced to a doping agent, giving it different electrical properties than the intrinsic (pure) semiconductor. ...
The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is by far the most common field-effect transistor in both digital and analog circuits. ...
If the gate material is polysilicon of opposite type to the body region, a spontaneous depletion region forms if the gate is electrically shorted to the substrate, in much the same manner as described for the pn-junction above. Polycrystalline silicon or polysilicon or poly-Si is a material consisting of multiple small silicon crystals, and has long been used as the conducting gate material in MOSFET and CMOS processing technologies. ...
Depletion width Depletion width describes the width of the depletion region in a semiconductor, particularly in geometries that are one-dimensional, like the pn-junction and MOS capacitor. The width of the depletion region is governed by the principle of charge neutrality. Two examples follow:
Depletion width in pn-junction The principle of charge neutrality in this case relates the depletion width wP in the p-region with acceptor doping NA to the depletion width wN in the n-region with donor doping ND: -
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- qNAwP = qNDwN.
This condition insures that the net negative acceptor charge exactly balances the net positive donor charge. The total depletion width in this case is the sum w = wN + wP.
Depletion width in MOS capacitor Again, the governing principle is charge neutrality. Let us assume an P-type substrate. If positive charge Q is placed on the gate, then holes are depleted to a depth w sufficient to expose sufficient negative acceptors to exactly balance the gate charge. Supposing the dopant density to be NA acceptors per unit volume, then charge neutrality requires the depletion width w to satisfy the relationship: -
-
- Q = qNAw
If the depletion width becomes wide enough in this case, electrons appear in a very thin layer at the semiconductor-oxide interface, called an inversion layer because they are oppositely charged to the holes that prevail in an P-type material. In this case, when an inversion layer forms the depletion width ceases to expand with increase in gate charge Q, and neutrality is achieved by attracting more electrons into the inversion layer instead. In the MOSFET this inversion layer is referred to as the channel. The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is by far the most common field-effect transistor in both digital and analog circuits. ...
See also This does not cite any references or sources. ...
There are very few or no other articles that link to this one. ...
Closeup of the image below, showing the square shaped semiconductor crystal various semiconductor diodes, below a bridge rectifier Structure of a vacuum tube diode In electronics, a diode is a two-terminal component, almost always one that has electrical properties which vary depending on the direction of flow of charge...
References - ^ Robert H. Bishop (2002). The Mechatronics Handbook. CRC Press. ISBN 0849300665.
- ^ John E. Ayers (2003). Digital Integrated Circuits: Analysis and Design. CRC Press. ISBN 084931951X.
- ^ Sung-Mo Kang and Yusuf Leblebici (2002). CMOS Digital Integrated Circuits Analysis & Design. McGraw–Hill Professional. ISBN 0072460539.
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