pn junction diode

do you know how actually pn junction diode work?

here i have the theory how it does..hehe..actually soalan ni ditanya masa aku g interview kt NS aritu..huhu..

In a p-n junction, without an external applied voltage, an equilibrium condition is reached in which a potential difference is formed across the junction. This potential difference is called built-in potential V_bi.
In an equilibrium PN junction (Figure 1.0), electrons near the PN interface tend to diffuse into the p region. As electrons diffuse

• they leave positively charged ions (donors) on the n region
• Similarly holes near the PN interface begin to diffuse in the n-type region leaving fixed ions (acceptors) with negative charge
• The regions nearby the PN interfaces lose their neutrality and become charged, forming the space charge region or depletion layer

Figure 1.0: A p-n junction in thermal equilibrium with zero bias voltage applied.

The electric field created by the space charge region opposes the diffusion process for both electrons and holes. There are two concurrent phenomena:

• the diffusion process that tends to generate more space charge
• and the electric field generated by the space charge that tends to counteract the diffusion.

The carrier concentration profile at equilibrium is shown in Figure 1.1 with blue and red lines. Also shown are the two counterbalancing phenomena that establish equilibrium.

A PN junction in thermal equilibrium with zero bias voltage applied. Under the junction, plots for the charge density, the electric field and the voltage are reported.

pn junction diode have 2 bias which are foward bias and reverse bias

• Forward-bias occurs when the P-type semiconductor material is connected to the positive terminal of a battery and the N-type semiconductor material is connected to the negative terminal. This reduces the width of the depletion zone.

• Connecting the P-type region to the negative terminal of the battery and the N-type region to the positive terminal, produces the reverse-bias effect. Therefore the depletion region widens