X-ray characterization of InAs laser structures grown by molecular beam epitaxy

An x-ray interference effect was used to characterize a set of strained layer laser structures containing N monolayers of InAs (N=1, 3, 5, 7) conveniently distributed in the quantum well active region. A sample containing 100 Å of Ga0.8In0.2As in the quantum well was also grown and characterized for comparison. Structural parameters such as thickness, chemical composition, and strain status of the different layers (cladding, waveguide, and quantum well layers) as well as the relaxation process and critical thickness due to increasing InAs content in the active region were studied. It was found that indium content was very close to the design values and that the whole structure is coherent with the substrate for 1 and 3 monolayers of InAs (and 100 Å of Ga0.8In0.2As) while the structure starts to relax by dislocation formation for 5 monolayers of InAs and is clearly relaxed for 7 monolayers of InAs. These x-ray results are in full agreement with transmission electron microscopy and characterization of the structures as laser devices.Peer Reviewe