Why direct band gap semiconductors are used in LED?

In direct band gap semiconductors most of the energy released after an electron in conduction band recombines with a hole in valence band will be in the form of light energy whereas In indirect band gap semiconductors most of the energy released after an electron in conduction band recombines with a hole in valence band will be in the form of heat energy Hence direct band gap semiconductors are used in Light emitting diodes. Some of the direct band gap semiconductors used in the manufacture of LED’s are direct band gap semiconductors gallium antimonide (GaSb), gallium arsenide (GaAs), indium phosphide (InP) e.t.c