What is charge density in PN junction?
What is charge density in PN junction?
As a result, the charge density of the P-type along the junction is filled with negatively charged acceptor ions ( NA ), and the charge density of the N-type along the junction becomes positive. This charge transfer of electrons and holes across the PN junction is known as diffusion.
What is current density in semiconductor?
Hence, the current density can be defined as the electric current carried by conductor per unit cross-sectional area of the conducting medium.
How does current flow through PN junction?
In a forward-biased PN junction, once the barrier voltage is overcome, it conducts a current. The externally applied potential pushes majority carriers toward the junction where recombination takes place, allowing current flow.
What is saturation current in PN junction?
The saturation current (or scale current), more accurately the reverse saturation current, is that part of the reverse current in a semiconductor diode caused by diffusion of minority carriers from the neutral regions to the depletion region. This current is almost independent of the reverse voltage. (
Why pn junction is called a diode?
A diode is called a diode because it has two distinct electrodes (i.e. terminals), called the anode and the cathode. A diode is electrically asymmetric because current can flow freely from the anode to the cathode, but not in the other direction.
Why is PN junction used?
When the diode is forward-biased, it can be used in LED lighting applications. It is used as rectifiers in many electric circuits and as a voltage-controlled oscillator in varactors….Applications of PN Junction Diode.
| Semiconductor Diode | Zener Diode |
|---|---|
| Extrinsic Semiconductors | Electric Field Lines |
Does current density depend on area?
The current density in a conducting wire depends on the current through the conducting wire and the cross-sectional area of the wire. For a given current, as the diameter of the wire increases, the charge density decreases. The current density is proportional to the current and inversely proportional to the area.
Why is current density important?
Densities in general are useful because they allow you to look at the effect of complicated distributions of the quantity in question (e.g. current,charge,mass) by adding up all the little current densities (Numerically or otherwise), current density allows you to find for instance the magnetic field inside a …
Does current flow from P to N?
the Conventional flow of current is from P side to N side. As in a forward bias p-n junction the electrons move from n side to p side , hence causing the conventional current flow from P to N . *Conventional current flow is always opposite to the direction of electrons flow.
Does current flow in reverse bias?
5.1. Reverse bias usually refers to how a diode is used in a circuit. If a diode is reverse biased, the voltage at the cathode is higher than that at the anode. Therefore, no current will flow until the electric field is so high that the diode breaks down.
Why it is called reverse saturation current?
In a PN junction diode, the reverse saturation current is due to the diffusive flow of minority electrons from the p-side to the n-side and the minority holes from the n-side to the p-side. it is a current which is produced due to the small reverse voltage when pn junction diode is reverse biased.
How do I calculate saturated current?
2 Answers
- Measure current with fairly large reverse bias, to give you Is. ( for example, -20V for a 1N4148)
- Measure forward voltage with fairly large forward current (for example, 20mA for a 1N4148) and calculate the emission coefficient: n=VFVT⋅ln(I/IS)
What is the saturation current density of a PN step junction?
Typical values of saturation current density for heterojunctions, pn step junctions and Schottky junctions on the example semiconductors (A/cm 2 ). The junction temperature is 300°K. (Note that the junction value for CdSe is valid for heterojunctions only, as p-type CdSe is not available)
What makes up the total current in a PN junction diode?
The total current flowing through the depletion region under forward biasing is made up of mostly majority carrier diffusion. When the diode is reverse biased diffusion is negligible, but drift remains constant. The total current flowing through the depletion region under reverse biasing is made up of mostly of minority carrier drift.
How to calculate the saturation current density of a heterojunction?
The estimated values of saturation current are presented in Table VI.13. Table VI.13. Typical values of saturation current density for heterojunctions, pn step junctions and Schottky junctions on the example semiconductors (A/cm 2 ). The junction temperature is 300°K.
How to calculate the saturation current density of a Schottky junction?
The saturation current density for a Schottky junction is: where λ is q/kT and the Richardson constant, A*, is given by: where m* is the effective mass of the majority charge carrier in the semiconductor (see Appendix B ). The quantity, ϕ Bn, is the barrier voltage adjusted for image force lowering (see Table VI.4 ).