Infrared light-emitting diode

An infrared light-emitting diode (LED), comprising

• a semiconductor light-emitting unit which includes:
• an active layer having a quantum well structure which includes at least one pair of layers, each pair of layers including a well layer and a barrier layer;
• a first waveguide layer and a second waveguide layer respectively disposed on two opposite sides of said active layer, and independently made of a semiconductor compound represented by (AlX3Ga1-X3)Y1In1-Y1P, wherein 0≤X3≤1 and 0<Y1≤1;
• a first cladding layer disposed on said first waveguide layer opposite to said active layer;
• a second cladding layer disposed on said second waveguide layer opposite to said active layer;
• and
• a current spreading layer disposed on said first cladding layer opposite to said first waveguide layer, made of gallium phosphide, and having a roughened surface opposite to said semiconductor light-emitting unit, said roughened surface having a surface roughness which ranges from 100 nm to 300 nm,
• a substrate which is light-transmissive and which is bonded to said current spreading layer opposite to said semiconductor light-emitting unit, and
• a bonding layer which is light-transmissive and which is disposed between said roughened surface of said current spreading layer and said substrate to bond therewith, said bonding layer being made of silicon dioxide and having a thickness which ranges from 1 μm to 5 μm.