Formation of a PN Junction Diode and its Band Diagram !

In order to initiate the junction formation, click the FormJunction button OR mouse drag one object toward the other. To return the semiconductor to separate pieces, click the Separate button OR drag one object away from the other:

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A click on a button will show an animated formation of PN junction diode, a snapshot of which is:

The red rectangle represents a p-type semiconductor and the blue rectangle an n-type semiconductor. At the moment, three semiconductors, Si, Ge and GaAs, have correct materials parameters. You can change the doping level by typing in the value and clicking the 'setNewValue' button.

Equilibrium band diagrams appear below the semiconductor. The green horizontal line is the Fermi level. Initiate the pn junction formation by clicking the 'FormJunction' button or using mouse drag and watch the physical system approach a new (electro-thermal) equilibrium which is characterized by a constant Fermi level throughout the material. The white region between the red (p-type) and blue (n-type) regions is the transition (or depletion) region where most of the free carriers are depleted. This white region is the space charge region with uncompensated ionized impurity charges which produce electric field in this region.

Space charge and electric field

Diffusion and drift currents

Applied bias and current flow

The SPICE device model for junction diode