Phonon contribution to metalorganic chemical vapor deposited Alx Ga1−xAs-GaAs quantum-well heterostructure laser operation

A series of experiments have been conducted to determine the extent of longitudinal optical (LO) phonon contribution to quantum-well-heterostructure (QWH) laser opertion. Extensive data are presented on metalorganic chemical vapor deposited (MO-CVD) AlxGa1−x As-GaAs QWH’s with active regions consisting of larger quantum wells, or in some cases bulk layers (Lz≳500 Å), coupled to phonon-generating and -reflecting arrays of coupled smaller quantum wells. Because of the electronic and vibrational coupling of the single larger layer to the array, the spontaneous emission and laser emission from these structures differ from that of QWH’s containing either a single well or a multilayer of uniform well thickness. In fact, phonon sideband laser operation of the larger GaAs layer can be induced at h/w∼Eg-h/wLO (undoped layers, nd−na≲1015 /cm3). An increase in either the thermal or nonthermal phonon occupation number is shown to cause phonon sideband laser operation in a QWH. A guide to the design of the multilayer array also is presented.