Semi Physics

This App is meant as a supplement to chapters on Semiconductor Physics, PN Junctions, NPN and PNP transistors.

It helps to show some concepts that maybe difficult to comprehend from a static picture in a textbook. The interface allows you to play the images or you can step forward and backward through the images.

There are 4 separate image sequences that are selected by a segmentation control on the lower right of the control panel.

SEMI
It shows the creation of both the valence and conduction energy bands.
Electron-hole pair creation and electron transport in both the valence and conduction energy bands.

How N-type and P-type silicon is created and the associated change to the energy bands. Also shows the Fermi distribution function and carrier density graphs and how they change with doping and temperature.

DIODE
It shows the creation of the depletion layer, electric field, charge density and built-in voltage from an abrupt PN junction with equal doping in both N and P side with a neutral bias.

An applied reverse bias shows the increased depletion layer, electric field, charge density and built-in voltage and equilibrium current.

An applied forward bias shows the decreased depletion layer, electric field, charge density and built-in voltage and significant forward bias current.

NPN
An NPN transistor in common-base configuration is first shown in an equilibrium state. Then in the normal active mode with the emitter-base junction forward biased and the base-collector junction reverse biased. It then shows the flow of electrons from the emitter to the collector along with the very small amount of base current. This demonstrates how the emitter to collector current is controlled by the amount of forward bias on the emitter-base junction.

PNP
A PNP transistor in common-base configuration is first shown in an equilibrium state. Then it in the normal active mode with the emitter-base junction forward biased and the base-collector junction reverse biased. It then shows the flow of holes from the emitter to the collector along with the very small amount of base current. This demonstrates how the emitter to collector current is controlled by the amount of forward bias on the emitter-base junction.

Note:
This is a now a free App but uses interstitial ads that will display, if available, after the segmentation control is selected. There are no banner ads and no in-app purchases.

更新履歴
This app has been updated by Apple to display the Apple Watch app icon.

Compiled for iOS8.3
Slider control programming changed so faster image play is set by slider farther to the right, slower to the left.
Slider value reset to nominal after selecting a new set of images from the segmentation control.