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Measurement of Band Gap in Semiconductors.


Using infra red absorption.

Basically Light of short wavelength .i.e. high energy, raises electrons to a higher band, so the light is absorbed by the semiconductor, while light without enough energy to raise electrons to the next band will pass through the semiconductor. This will be a simulation of an experiment to measure the band gap of various samples of semiconductor's several have quantum wells, the confinement energy of the wells can be calculated as a simple particle in a square well.

The experiment uses a wide bandwidth quartz light and a Jyobin von monochromatic/spectrometer, to produce monochromatic light between 400 nm and 1200 nm. The light passing through the semiconductor is measured with a Hamatsu photodiode, this is a silicon photodiode so the band gap measurement is limited by the band gap of the silicon.
The electronics are quite simple. A chopper and lock in amplifier make sure the signal from the photodiode is not due to extraneous light. The monochromator is controlled by a PC the PC also reads the voltage produced by the photodiode.
I wrote a program in Visual Basic to control the PC, I still have a set of data files from a range of about 6 samples. I will rewrite the program to act as a simulator and include the data files.

This will be continued when I can dig out the data files and other information.

     
       

 

 
     
  Cobbled together on the {1st May 1999}
by
Richard

{last modified {4th Dec 2000}}