Direct and indirect semiconductors, Electrical Engineering

Direct and Indirect Semiconductors

1) In a common quantitative calculation of band structures, the wave function of a single electron traveling by a perfectly periodic lattice is assumed to be in the type of a plane wave moving in the x-direction (say) with propagation constant k, as well called a wave vector.

2) In quantum mechanics, the electron momentum can be provided by p= hk.

3) The wave function that is space dependent for the electron is ΨK (X) = U (Kx,x) ejK,x  in which the function U(Kx,x) modulates the wave function as per to the periodicity of the lattice.

4) Allowed values of energy, where as plotted as a function of k, gives the E-k diagram.

5) As the periodicity of most lattices is different in several directions, the E-k diagram is a complex surface that is to be visualized in three dimensions.

6) Direct band gap semiconductor: the minima of the conduction band and the maxima of the valence band take place at the same value of k => an electron creating the smallest energy transition from the conduction band to the valence band can do so with no a change in k (and, the momentum).

1968_Direct and Indirect Semiconductors.png

Figure:  Direct and indirect transition of electrons from the conduction band to the valence band:  (a) direct - with accompanying photon emission, (b) indirect via defect level.  

7) Indirect band gap semiconductor: the minima of the conduction band and the maxima of the valence band take place for different values of k, so, the smallest energy transition for an electron needs a change in momentum.

8) Electron  that falling  from  conduction  band  to  an  empty  state  in  valence  band => recombination.

9) Recombination possibility for direct band gap semiconductors is much higher than as compared to that for indirect band gap semiconductors.

10) Direct band gap semiconductors give up the energy released throughout this transition (=Eg) in the form of light => employed for optoelectronic applications (e.g., LEDs and LASERs).

11) Recombination in indirect band gap semiconductors takes place by some defect states within the band gap, and the energy is released in the type of heat given to the lattice.

 

Posted Date: 1/11/2013 3:09:24 AM | Location : United States







Related Discussions:- Direct and indirect semiconductors, Assignment Help, Ask Question on Direct and indirect semiconductors, Get Answer, Expert's Help, Direct and indirect semiconductors Discussions

Write discussion on Direct and indirect semiconductors
Your posts are moderated
Related Questions
Discuss the following points with regard to the Company selecting Jebel Ali Free Zone as its Middle East base.  (a) How is a company likely to enhance its supply chain by using

What is the main thing to look for in calculations of air gaps?

#Minimum 100 words accepted#explain depletion operations of MOSFET

What is the power of the signal transmitted by powerful cell phones? Ans) The powerful cell phones can transfer a signal of 3 watts.

Analysis of Frequency Response with PSpice and PROBE PSpice can readily accomplish the circuit analysis as a function of frequency, and PROBE can display Bode plots for magnitu

Q. Explain common base configuration? Common-base transistor amplifiers are so-called because the input and output voltage points share the base lead of the transistor in commo

Q. A filter is a network employed to select one range of frequencies while rejecting all other frequencies. A basic building block often used in integrated-circuit filters is shown

Active-mode NPN transistors in circuits Figure:  Structure and use of NPN transistor. Arrow according to schematic. The figure opposite is a schematic presentation

Consider the circuit shown in Figure with R 0 , (b) the quality factor Q, and (c) the maximum impedance Z m . Comment on the applicability of the universal resonance curve.

Consider a forward-biased diode with a load resistance. Let the static volt-ampere characteristic of the diode be given by Equations, and typically represented by Figure. (a) Fo