24-07-2012, 04:03 PM
Photodetectors
Photodetectors (1).ppt (Size: 324 KB / Downloads: 240)
The side is on the order of less than a micron thick (formed by planar diffusion into n-type epitaxial layer).
A space charge distribution occurs about the junction within the depletion layer.
The depletion region extends predominantly into the lightly doped n region ( up to 3 microns max)
Electrodes in the diagram are the external contacts.
The degree to which photons penetrate through the layers is dependant upon radiation wavelength.
The E field separates the electron and hole and causes them to drift in opposite directions until they reach neutral regions.
The drifting carriers generate a photocurrent in the external circuit developing an electrical signal.
The photocurrent exist for a time frame equal to the time it takes for the electron and hole to cross the depletion layer (W) and arrive at the neutral region.
The magnitude of the photocurrent ( ) is dependant on the number of EHPs generated and the drift velocities of the carriers while moving across the depletion layer.