SEMI-CONDUCTOR DIODE

A diode is a one way device that allows electric current to flow through only one direction
(forward biased) and will prevent current from passing through the reverse direction (reverse biased).  

DOPING OD A DIODE 

A diode is made from an intrinsic semiconductor material that will not conduct unless impurities are added. Therefore, doping is the process of adding impurities to the semi-conductor material to alter their properties and make it conduct.

P-N JUNCTION 

A diode is usually doped with two different kinds of impurities. This produces two types of doping called N-type and P-type doping.

In N-type, Phosphorous (with five outer electrons) is added to the silicon thereby giving it 1 extra electron.

In P-type, Boron (with three outer electrons)  is added to the silicon thereby giving it 1 extra ‘hole’ 

Therefore, a P–N junction is a boundary or interface between two types of semiconductor materials, P-type and N-type, inside a single crystal of semiconductor.

DIFFERENCES BETWEEN FORWARD BIAS AND REVERSE BIAS IN DIODE 

• In forward bias, positive terminal of a battery is connected to the P-type and negative terminal is connected to the N-type semi-conductor. While in reverse bias, the positive terminal of the battery is connected to the N-type and the negative terminal is connected to the P-type semiconductor.

• In forward bias, depletion layer is very thin. While in reverse bias, depletion layer is very thick

• In forward bias, P-N junction offers very low resistance. While in reverse bias, the P-N junction offers very high resistance.

• In forward bias, an Ideal diode has zero resistance. While in reverse bias, an ideal diode has infinite resistance.