For manufacturing the light emitting diodes (LEDs) the germanium and silicon semiconducting materials are not used because these are heat producing materials. These materials are very poor in emitting light radiations.
The semiconducting materials used for manufacturing visible LEDs are gallium phosphide (GaP), Gallium Arsenide Phosphide (GaAsP) and gallium nitrate (GaN).
The LEDs are radiate lights in different colors such as red, green, yellow, blue, orange, etc. The GaAsP emits either red or yellow light. GaP emits red or green light and GaN emits blue light.
The best semiconductor material used for manufacturing infra red (IR) LEDs is gallium arsenide (GaAs).
The constructional diagrams of LEDs are fabricated by using vapors phase or liquid phase epitaxial.
Direct band gap red LED are fabricated on a GaAs substrate and indirect band gap LEDs are a GaP substrate. Indirect band gap LEDs emits orange, yellow or green light. Here an N type layer.
The metal connection to both the layers make anode and cathode terminals and indicated. The transparent window is provided at the top of the surfaces.