PIN Diode

In PIN diode the i region is sandwiched between the p and n region as shown in Fig 11.5

The i-region is either a high resistivity layer.

PIN diodes are fabricated by

-epitaxial process

-Diffusion of p and n in high resistability substrate

-ion drift method

The concentration, charge density and electric field profiles are shown in Fig 11.6

PIN diodes are used widely in microwave wave circuits such as microwave switch with constant depletion layer and high power.

The switching speed

Where W is the total depletion region width and is the saturation velocity across i region.

In addition the PIN diode can be used as

-variable attenuator by varying device resistance that change approximately likely with forward current

-Modulate signals up to GHz range.

-Photo detection of internal modulated light in reverse bias.

Under Riverse Bias the junction capacitance is

and the series resistance is

Where is the i-region resistance and is the contact resistance.

The reverse bias current is

Where is the ambipolar life time. The I-V characteristics is shown in Fig 11.7