Semiconductor equations, Electrical Engineering

Semiconductor Equations 

The semiconductor equations that are relating these variables are shown below:

Carrier density:

n = ni exp (EFN - Ei / KT)        (1)

p = ni exp (Ei - EFP / KT)        (2)

In which EFN is the electron quasi Fermi level and EFP is the hole quasi Fermi level. These above 2 equations lead to 

Np = n­i2 exp (EFN - EFP/ KT)   (3)

In equilibrium EFN = EFP = Constant

Current:

There are two mechanism of current; electron current density and hole current density. There are various mechanisms of current flow:

  1. Drift
  2. Diffusion
  3. Thermionic emission
  4. Tunnelling

The final two mechanisms are significant frequently only at the interface of two different materials like a metal-semiconductor junction or a semiconductor-semiconductor junction where the two semiconductors are of dissimilar materials. Tunneling is as well significant in the case of PN junctions in which both sides are heavily doped.

The dominant conduction mechanisms include drift and diffusion in the bulk of semiconductor. The current densities because of these two mechanisms can be written as

JN = qnμNε + qDN dn/dx   (4)

JP = qnμPε + qDP dP/dx   (5)

In which μN and μP are electron and hole mobilities correspondingly and DN, DP are their diffusion constants.

Potential:

The potential and electric field in a semiconductor can be described in the following ways:

  1. Ψ = - EC /q + constant ; ε =  (1/q) (dEc / dX)
  2. Ψ = - EV /q + constant ; ε =  (1/q) (dEV / dX)
  3. Ψ = - Ei /q + constant ; ε =  (1/q) (dEi / dX)
  4. Ψ = - EO /q + constant ; ε =  (1/q) (dEO / dX)

All these definitions are equal and one or the other may be selected on the basis of convenience. The potential is connected to the carrier densities through the Poisson equation: -

2 Ψ / ∂X2 = - q/ε (p-n+ N+D - N-A)      (6)

In which the last two terms present the ionized donor and acceptor density.

 

Posted Date: 1/11/2013 2:11:47 AM | Location : United States







Related Discussions:- Semiconductor equations, Assignment Help, Ask Question on Semiconductor equations, Get Answer, Expert's Help, Semiconductor equations Discussions

Write discussion on Semiconductor equations
Your posts are moderated
Related Questions

Two sine waves along with periods of 10 ms and 30 ms are added to generate a single waveform. A spectrum analyzer is utilized to examine the frequency contents of the waveform. Wha

Q. Given the K map of a logic function as shown in Figure, in which ds denote don't-care conditions, obtain the SOP expression.

Design and simulate by using multisim software a series voltage regulator to supply 1A to a load at a constant voltage of 9V. The supply voltage to regulator is 15V±10%. The minimu


What makes them sine? Ans) Fourier tells that only a sine wave has no harmonic content. The math works out that if you have any wave shape other than a sign wave, you can brea

In terms of negative feedback, there exists an analogy between the operational amplifier and the power-steering mechanism of an automobile. The hydraulic pump is analogous to the p

Q. Explain various functions of telephone switching systems. Ans: Functions of telephone switching systems are: (i)  Attending: The system should be continually monito

What is Threaded system. Threaded system: At times we require implementing an operating system which can process multiple threads. Many threads are handled through the kernel

What are the different kinds of surface entities used in CAD? Give homogeneous Matrix form equation for : (i) B-Splive Curve (ii) Bezier Curve