If there was only one side of cladding material, the device would be a simple, or single, heterostructure.
The double heterostructure is a very useful structure in optoelectronic devices and has interesting electronic properties.
If one of the cladding layers is p-doped, the other cladding layer n-doped and the smaller energy gap semiconductor material undoped, a p-i-n structure is formed.
When a current is applied to the ends of the pin structure, electrons and holes are injected into the heterostructure.
The electrons and holes recombine in the intrinsic semiconductor emitting photons.