Gap Band Essay examples

2333 Words Oct 18th, 2013 10 Pages
Factors Affecting the

Band Gap of LEDs

By Mohammad Reza Farham

Chemistry 222 Thursday 08.02.2012

Lab Partner: Thanh Nguyen
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Data shows GaP0.40As0.60 and GaP0.65As0.35 have shorter wavelengths and larger band gaps when the temperature is lowered.
15. A student has claimed that when a material is cooled, a substance usually contracts because the bonds between the atoms get shorter. Using only data directly from this experiment, either support or refute this student’s claim. Supported. When the material is cooled, the Eg increased. Increasing Eg may result from a shorter bond distance (greater orbital overlap). The data supports, but does not prove this claim.

16. A different student has claimed that when a material is cooled, the resistance of a metal should effectively increase, because the electrons must be moving slower due to the low temperature. Using only data directly from this experiment, either support or refute this student’s claim. Refuted. The data shows that metals decrease their resistance when cooled.
17. Suggest a hypothesis that would explain your answer to Question 16. 

Most likely, there is less scattering of electrons by the metal atoms at cool temps because they don’t vibrate as much on their lattice positions.
18. Based only on the data from Experiment 4, state a claim about the relationship between the conductivity (ease of electron flow) of a semiconductor in the light compared to in the dark. Be sure to explicitly show (or reference) the data used to suggest your claim. Data Conductivity of a

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