Types of Noise

The main sources of noise in semiconductor devices are:

1	Thermal Noise is due to the Johnson effect in the ohmic regions. It is practically frequency independent.

2	Shot Noise is due the diffusion and passage of carriers across barriers. This noise can be represented by independent random events. Its spectral distribution depends on the bias current and is frequency independent.

3	Burst Noise is due to the capture and emission of carriers in localized traps causing a fluctuation between current levels. It is usually present in small devices and Si-SiO2 interfaces (e.g. MOS).

4	1/f Noise (also called Flicker Noise) is believed to be caused by surface recombination due to traps and defects in the crystal.