To emit red or green light, LED is manufactured using

Light Emitting Diodes (LEDs) require semiconductors with a specific band gap to emit visible light (typically between $1.8\text{ eV}$ and $3.0\text{ eV}$).

The compound semiconductor Gallium Arsenic Phosphide (GaAs_{1-x}P_x$) is widely used for manufacturing LEDs of various colours. The emission wavelength depends on the band gap, which can be tuned by varying the composition ratio of Arsenic to Phosphorus (x$).

For instance, $GaAs_{0.6}P_{0.4}$ has a band gap of approximately $1.9\text{ eV}$ and is used to emit red light. By increasing the phosphorus content, the band gap increases, allowing the LED to emit higher-energy visible light, such as green.

Therefore, Gallium Arsenic Phosphide is used to manufacture LEDs that emit red or green light.

Answer: gallium arsenic phosphide.