This program enables students to learn about energy bands in a number of semiconductor devices. Two cubes each representing pieces of semiconductor material are displayed on either side of the screen. The energy band diagram for each cube is displayed directly below it. Impurities (donors and/or acceptors) can be added to each side, and the resulting change in the energy band diagram can be observed directly below each cube. The student then brings the material together and can create a number of p-n junction devices.
The program simulates Light Emitting Diodes (LEDs), solar cells and tunnel diodes. A voltage can be applied across the device directly, which can be changed using a scrollbar or the device can be used in a simple circuit with a resistance and a potentiometer. The current through the circuit can be changed by "turning" the potentiometer knob, just as the student would do in a laboratory experiment. In either case the student can observe the resulting change in the energy band diagram of the p-n junction device. In an adjacent frame the student can also observe the current - voltage graph of the device being generated as the voltage is changed or the potentiometer knob is "rotated". In case of the LED, the resulting intensity spectrum of the emitted light of the LED can also be observed in an adjacent frame, while for the solar cell, the student can alter the intensity spectrum of the incident light, and observe the resulting change in the energy band diagram and/or current-voltage graph.
This program bridges a gap between the students understanding of energy band diagrams and their influence on the observable electrical and/or spectral properties of some semiconductor devices. The student can change a wide range of parameters including the type of semiconductor, temperature, dopant density, and p-n junction area. An advanced student can also create her/his own hypothetical semiconductor with any desired carrier effective mass, mobility or energy band gap. All these features make this program a versatile tool useful both for the beginner and advanced student alike. In several respects it fills a void left by other more advanced circuit simulator programs that appeal only to more advanced students and do not seek to explain the physics of devices that are used in circuits.