This applet displays a wealth of information about the relationships between density of states, Fermi level and distribution, density of occupied states of both electrons and holes in a semiconductor, and temperature. Users can interact with the applet, changing the temperature and Fermi level. Supplementary material includes brief tutorials and mathematical analysis.
To understand how the concentration of current carriers in a semiconductor changes with temperature and location of the Fermi energy.
Target Student Population:
Upper level undergraduate and graduate solid state, electronic devices course
Prerequisite Knowledge or Skills:
Nature of the Fermi-Dirac distribution, definition of density of states, simple band structure, and law of mass action.
Content Quality
Rating:
Strengths:
The variation of carrier concentration in both the conduction and valence bands with Fermi energy and temperature is presented in an effective manner. The law of mass action is nicely demonstrated. This applet presents in a very visual fashion multiple concepts that students typically have difficulty understanding. The physics involved in establishing carrier concentration is effectively presented.
If you teach solid state physics, you will love this Applet.
Concerns:
Several of the standard links used on this site (applet tutorial, applet worksheet, quiz, SPICE simulation) are to empty pages. The one reference given is not on-line.
Potential Effectiveness as a Teaching Tool
Rating:
Strengths:
Recommended Use(s) for Material: Lecture/Demo, Tutorial
The law of mass action is not one of the more easily visualized concepts presented in solid state physics. This Applet renders that topic much more accessible. The dependence of carrier concentration on both temperature and Fermi energy is presented in an extremely effective way. The energy distribution of the carrier density is particularly informative, in part because of its simple display.
Concerns:
Use(s) Material is not Suited For: Homework, Quiz/Test (without substantial instructor-added material)
The applet has the flexibility to show or hide various functions (density of states, Fermi distribution, density of occupied states). However, the instructor will need to spend time explaining what is being shown, particularly for the left graph with both the density of states and the fermi distribution, because of the large amount of information. The textual information currently in the introduction and mathematical analysis is not sufficiently clear for most students to understand the display on their own.
Ease of Use for Both Students and Faculty
Rating:
Strengths:
The accompanying five-minute tutorial is complete and the learning curve for this applet is easily mastered. The tutorial was entirely self-contained with appropriate references and links.
Concerns:
The information shown in default mode of the left display is much too dense, making the display hard to read and interpret.
General Comments on Usability: The applet is simple to use, though not so simple to interpret. For demonstration purposes or for student self-study a default mode of displaying less information would be more convenient. The limitations of HTML result in sometimes confusing notation in the Introduction and Mathematical Analysis parts.
Creative Commons:
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