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
Q. Counting to moduli other than 2 n is a frequent requirement, the most common being to count through the binary-coded decimal (BCD) 8421 sequence. All that is required is a four

Selection of Proper Fuse : Fuse is a safety device or a wire of metal in a cut-out which may be fused by an excessive current. The current drawn by an appliance is restricted by t

What are the cautions to be taken before starting work on electrical installations? Ans: Before starting any electrical works on installations disconnect the power supply to

Digital Transmission on Fading Multipath Channels We have discussed thus far digital modulation and demodulation methods for the transmission of information over two types of c

Explain Memory Mapped I/O Scheme. Memory Mapped I/O Scheme: In this scheme there is only one address space. Address space is explained as all possible addresses which microproc

Define Johnson Counters to Make Simpler Combinational Logic? The ring counter technique able to be efficiently utilized to implement synchronous sequential circuits. A main pr

Q. What do you mean by Number Systems? The Digital circuits are inherently binary in nature, but numerous types of representations of numerical data are in use. The represen


Atoms with four valence electrons are good conductors. This statement is true or false. Ans:  Atoms are good conductors with four valence electrons. This statement is false.

Q. Explain about Stored Program Control? Stored Program Control:   In centralized control, all control equipment is replaced by a single processor which should be quite powerf