Horst Baumeister

Comparison of structural and optical properties in strained GaInAsP MQW structures grown by MOVPE and MOMBE

Abstract The growth parameter dependence of the transition from 2D to 3D growth of GaInAsP multiple quantum well (MQW) structures up to e B =0.5% tensile-strained barriers was examined. Identical MQW structures with e W =1% compressively strained wells were grown by metal organic vapor-phase epitaxy (MOVPE) and metal organic molecular beam epitaxy (MOMBE) and characterized by photoluminescence (PL), X-ray diffraction and transmission electron microscopy. Increasing the tensile barrier strain resulted in deteriorated optical and crystalline properties beyond a critical strain limit, which depends on growth temperature. The deterioration originates from lateral layer thickness and strain modulations. Their density, amplitude and thus their effect on the optical MQW properties are different for both growth methods. High-quality MOMBE-grown MQW structures up to e W =2% compressive well strain and e B =0.5–1% tensile barrier strain could be achieved by inserting thin intermediate layers at each internal interface. The composition of these intermediate layers has a significant effect on MQW material properties.

Heterointerface optimization in InP based strained MQW laser structures using metalorganic growth technologies

Epitaxial growth of InP based strained MQW laser structures is studied for metalorganic vapor phase epitaxy (MOVPE) and metalorganic molecular beam epitaxy (MOMBE or CBE-chemical beam epitaxy). For a tensile barrier layer strain of |/spl epsiv//sub B/|/spl ges/0.4% both in MOVPE and MOMBE, wavy MQW interfaces are observed in TEM along with a severe drop in photoluminescence (PL) intensity and an increase in PL FWHM (full width at half maximum) yielding a significant increase in threshold current density of broad area test lasers. Lateral thickness modulations appear to be much larger in MOVPE than in MOMBE. The V/III ratio appears to be a key parameter for the rate of wavy interface development, which is probably a consequence of surface selective growth. Flat interfaces require low V/III ratios, especially at high strain in the barrier layers resulting in a significant improvement in threshold current density.

Mechanisms in embedded selective epitaxy and overgrowth of an integrated laser/modulator quantum well structure using MOMBE and MOVPE

Lateral integration of optoelectronic devices comprising strained multiple quantum well (MQW) structures can most successfully be accomplished by selective area epitaxy using metal organic molecular beam epitaxy (MOMBE). We optimized the growth parameters with respect to a planar butt coupling and sharp, flat MQW interfaces in an integrated MQW laser / MQW modulator structure. Defect generation in metal organic vapor phase epitaxy (MOVPE) overgrown cladding layers is analyzed and shown to contain information about the quality of the buried butt coupling. A ridge waveguide structure has successfully been fabricated from an optimized integrated laser / modulator structure.