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Epitaxial growth of laterally structured lead chalcogenide lasers
Epitaktisches Wachstum von lateral strukturierten Blei-Chalkogenid-Lasern
Buried Heterostructure (BH-)Lasers based on PbEuSe were made using Molecular Beam Epitaxy (MBE). After growing the active layer of a DH-structure the growth was interrupted. By use of photolithography and Arplus-ion beam etching mesa stripes were defined and overgrown with a PbEuSe clad by a second MBE step. The overgrowth was investigated by scanning electron microscopy (SEM), using a selective chemical etch to clearly resolve areas of different Eu-content. The SEM pictures indicate the crucial role of the mesa shape for the overgrowth quality. Sharp edges result in deep cracks or grooves aside a well grown ridge. To optimize the active mesa shape a chemomechanical etch process was developed after the ion milling process. The obtained smooth mesa shape results in a better overgrowth. As an alternative approach for fabrication of BH-lasers shadow masked growth of the active mesa stripe was investigated. Masks with slits in the 10 mym range and sharp edges were obtained byanisotropic e tching of (100)-Si. BH-lasers with an active stripe width of 40 mym were made by this technique and showed a reduced threshold current compared to DH-lasers.