Stimulated emission in strained-layer quantum-well heterostructures

Stimulated emission data are presented on a large variety of strained-layer quantum-well heterostructures (QWH’s) and superlattices (SL’s) grown by metalorganic chemical vapor deposition (MOCVD). These structures consist of barrier-well combinations of thickness LB,Lz ≲150 Å made from GaAs-InGaAs, GaAsP-GaAs, and GaAsP-InGaAs. Also employed are higher band-gap confining layers of InxAlyGa1-x-yAs, AlyGa1−yAs1−xPx, and AlxGa1−xAs. All of the heterostructures are grown on a GaAs substrate with and, in some cases, without a graded layer. The strain range between 0.2 to 12.5×10−3 is examined. Photopumped, these heterostructures operate as continuous (cw) 300 K lasers, with thresholds of 1.6–7.5×103 W/cm2, for periods of time between 0.5 to >35 min. Under high-level excitation, the equivalent of Jeq∼103 A/cm2, laser operation fails or is quenched by networks of dislocations (with 〈110〉 Burger’s vectors) that are generated within the strained-layer region of the QWH’s or SL’s. These dislocation networks, which are revealed via transmission electron microscopy (TEM), occur at a more rapid rate in higher threshold samples and ones with higher built-in strain. The TEM data show, however, that no heterointerface defects (dislocations) are present in the as-grown strained-layer regions but are present in thick (bulk) graded regions.