Heterojunctions in Al_xGa_1-xAs-GaAs and related materials are being examined. Quantum size effects have been observed and have led to single and multiple active layer quantum-well diode light emitters and lasers. Stimulated emission, absorption, disorder, alloy clustering, carrier scattering, phonon processes, tunneling effects, and impurity diffusion in these structures are being studied. Impurity-induced disordering and Al-bearing native oxides are being studied and used to form stripe-geometry lasers and more complicated array structures. Quantum well lasers have been operated in an external grating cavity in an extended wavelength range. Newer forms of quantum-well lasers

Tony Minervini and Jon Wierer examine laser diode experiments, supervised by Professor Nick Holonyak, Jr.

have been realized, including native-oxide-defined lasers and waveguides.

The fundamental properties of III-V heterostructures grown by vapor phase epitaxy are being studied. On quantum-well MOCVD AlGaAs-GaAs heterostructures, laser operation 400 meV above E g (GaAs) has been observed, the first cw 300 K laser operation has been achieved, laser operation on phonon-sidebands below the confined-particle states has been observed, and alloy disorder and clustering in quantum well heterostructures have been identified. Impurity-induced disordering of quantum-well hetero structures and Al-bearing native oxides, e.g., the native oxide of Al_xGa_1-xAs formed at 400° to 500°C with H₂O + N₂, are being examined via TEM and photoluminescence studies. This project is the first (1977) to realize p-n quantum-well lasers and to ``coin'' the name ``QW lasers.''