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Unformatted text preview: Interactive Exercises for Use with Excel Spreadsheets on Semiconductor Device Theory IMPORTANT NOTE FOR ALL SPREADSHEETS & EXERCISES : If you are accessing any of the spreadsheets over the Internet from within Internet Explorer, the interactive dialog box will not work because ActiveX controls are automatically disabled. To work properly, the spreadsheet must be downloaded to your computer first (usually by right-clicking on it). 2 nd IMPORTANT NOTE FOR ALL SPREADSHEETS & EXERCISES : You must launch Excel BEFORE loading the spreadsheet, and select Tools/Macro/Security to set the security level to Medium so that macros can be enabled. Otherwise the spreadsheets will not function properly. Then, after opening the spreadsheet on your local drive, click Enable Macros when asked. The built-in Help function is an excellent source of information on Excel.) 1 . Fermi-Dirac Distribution Function . Use the spreadsheet Distribution Functions to complete the following exercise: After opening the spreadsheet, click on the Fermi-Dirac sheet to see a plot of the Fermi-Dirac function. You may also want to look at the corresponding data sheet (with the same colored tab); you may have to scroll across and/or down to see all the calculated values. Cells with a red tab in the corner have comments defining or explaining the contents of that cell; you can see these by hovering over the cell with the cursor. Click on the Show Options button on the plot to bring up the plot controls (note they are on a tabbed dialog box). You can drag the box out of the way to see the plot. Click the Restore Defaults button to initialize the default settings. The horizontal axis is energy in units of eV, measured from the Fermi level. Use the scroll bar to change the temperature (you can click on the bar, drag the button, click on the arrows, or type a specific number in the box) and observe the effects. Note that E F itself may change with temperature, but that cannot be observed here because everything is shown relative to E F . a) Using the spreadsheet, find the probability that an allowed state i) at the Fermi level; ii) 0.1 eV above E F ; and iii) 0.1 eV below E F is occupied by an electron at a temperature of 300 K (about room temperature). You should use the data sheet to get accurate values (dont just read them off the plot, though you can check them approximately that way). You can set the value of T either using the Options box on the Fermi-Dirac plot, or by entering it directly on the Materials sheet. However , there are two different temperatures on the latter sheet; you must set the Temperature for Fermi-Dirac plot, NOT the Temperature for gc/gv plot. b) Check at least one of the calculations in part (a) by hand, and show your work in doing so....
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- Spring '10