The phonon‐assisted laser operation (4.2–77 °K) of multiple quantum‐well AlxGa1−xAs‐GaAs heterostructure diodes is described. Laser operation is observed on phonon sidebands ∼36 meV below the lowest confined‐particle transitions. Tunnel injection into the confined‐particle states, with light emission and negative‐resistance regions, is also observed in these multiple quantum‐well heterostructures. Two different multiple quantum‐well heterostructures grown by metalorganic chemical vapor deposition are described. The first consists of six GaAs quantum wells (Lz∼120 A˚) coupled by five AlxGa1−xAs (x∼0.3) layers (∼120 A˚), and the second is similar except for a reduction in layer size to ∼50 A˚.