CONSTRUCTION OF LED

 SUBSTRATE MATERIAL - The materials are sapphire, SiC etc.

 SEMICONDUCTOR MATERIAL - Indium gallium nitride (InGaN) for Blue, Green, Ultraviolet high brightness LEDs. Aluminum gallium indium phosphide (AlGaInP) for Yellow, Orange, Red high brightness LEDs.

CONSTRUCTION :

      1. A  n - type semiconductor layer is placed on the substrate .

      2. A   p - type semiconductor layer is placed on the  n - type layer by diffusion .

      3. The carrier charge recombination is take place in the  p - type layer . So, the  p -type layer is placed on the TOP.

     4. For the maximum light emission , a metal film (aluminum) anode is placed at the outer edges of the  p - type layer.

     5. The bottom of the substrate  is coated with the metal film (gold) for to reflect most of the light to the surface of the device and provide the cathode connection.

       The above points will give the basic idea about the construction of LED.