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We investigate optical transitions and carrier dynamics in hybrid structures containing type-I GaAs/AlGaAs quantum wells (QWs) and type-II GaSb/AlGaAs quantum dots (QDs). We show that the optical recombination of photocreated electrons confined in the QWs with holes in the QDs and wetting layer can be modified according to the QW/QD spatial separation. In particular, for low spacer thicknesses, the QW optical emission can be suppressed due to the transference of holes from the QW to the GaSb layer, favoring the optical recombination of spatially separated carriers, which can be useful for optical memory and solar cell applications. Time-resolved photoluminescence (PL) measurements reveal non-exponential recombination dynamics. We demonstrate that the PL transients can only be quantitatively described by considering both linear and quadratic terms of the carrier density in the bimolecular recombination approximation for type-II semiconductor nanostructures. We extract long exciton lifetimes from 700 ns to 5 μs for QDs depending on the spacer layer thickness. [ABSTRACT FROM AUTHOR]

We report the device characteristics of GaInSb/AlGaSb quantum well (QW) lasers monolithically grown on GaAs substrates by using an interfacial misfit (IMF) array. The IMF array localized at the GaSb/GaAs interface can accommodate the 7.8% lattice mismatch between GaAs substrates and GaSb buffer layers, resulting in the formation of a GaSb buffer with a very low defect density on GaAs substrates. Top-top and top-bottom metal contact methods are applied to the Ga0.9In0.1Sb/GaSb QW edge-emitting lasers monolithically grown on GaAs substrates for characterizing current–voltage ( I– V) and output power–current ( L– I) curves. The potential drop at the IMF array of ~0.7 V is elucidated by comparing I– V characteristics with these two contact methods. L– I characteristics and electroluminescence spectra shows room-temperature lasing at 1.83 μm from a 1.25-mm-long top-top contact device containing six-layer Ga0.9In0.1Sb QWs with a threshold current density ( J th) of 860 kA/cm2. This IMF technique will enable a wide range of lasing wavelengths from near- to mid-wavelength infrared regimes on a GaAs platform. [ABSTRACT FROM AUTHOR]

Fabrication of microcylinder laser cavities in III-Sb material on a silicon substrate is reported. Room temperature lasing near 2 μm wavelength under optical pumping conditions is demonstrated in the microcylinders with InGaSb quantum wells. The III-Sb material is grown monolithically on a silicon substrate. High quality epitaxy is enabled by an interfacial misfit array. [ABSTRACT FROM AUTHOR]

The authors report the device characteristics of GaInSb/AlGaSb quantum well (QW) lasers monolithically grown on GaAs substrates. The 7.8% lattice mismatch between GaAs substrates and GaSb buffer layers can be completely accommodated by using an interfacial misfit (IMF) array. Room-temperature lasing operation is obtained from a 1.25-mm-long device containing six-layer Ga0.9In0.1Sb/Al0.35Ga0.65Sb QWs at 1.816 μm with a threshold current density of 1.265 kA/cm2. The observed characteristic temperature and temperature coefficient are 110 K and 9.7 Å/K, respectively. This IMF technique will enable a wide range of lasing wavelengths from near-infrared to midwavelength-infrared regimes on a GaAs platform. [ABSTRACT FROM AUTHOR]

The authors report the optical characteristics of GaSb/GaAs self-assembled quantum dots (QDs) embedded in an InGaAs quantum well (QW). Variations in the In composition of the QW can significantly alter the emission wavelength up to 1.3 μm and emission efficiency. Lasing operation at room temperature is obtained from a 2-mm-long device containing five stacked GaSb QDs in In0.13Ga0.87As QWs at 1.026 μm with a threshold current density of 860 A/cm2. The probable lasing transition involves electrons and holes confined in the QW and QDs, respectively, resulting in a large peak modal gain of 45 cm-1. A significant blueshift of the electroluminescence peak is observed with increased injection current and suggests a type-II band structure. [ABSTRACT FROM AUTHOR]

The authors demonstrate a monolithic, electrically injected, vertically emitting GaSb/AlGaSb light emitting diode (LED) emitting at 1.6 μm comprised of a hybrid GaAs/GaSb-based structure. The LED is comprised of a GaSb/AlGaSb quantum well/barrier active region embedded within high index contrast GaAs/AlGaAs distributed Bragg reflectors (DBRs) using two interfacial misfit (IMF) arrays to relieve the strain induced from the high 8% lattice mismatch between the material systems. The first IMF is formed under compressive strain conditions to enable strain-free, defect-free deposition of GaSb active region directly on the lower GaAs/AlAs DBRs without need for thick buffer. The second IMF is formed under tensile conditions to enable the upper GaAs/AlAs DBRs on the GaSb active region. The device demonstrates a maximum output power of 3.5 μW. Initial diode optical and electrical characteristics along with IMF band structure are discussed. [ABSTRACT FROM AUTHOR]

Ring and stripe oxide-confined vertical-cavity surface-emitting lasers are studied. Interesting coupling effects are observed due to the nonzero propagation velocity of the optical mode in the plane of the cavity. The stripe geometries appear interesting due to the very low threshold and provide a convenient means for increasing the aperture size while maintaining uniform current pumping. The ring laser provides a means of obtaining well defined multiple spots in the far field. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Monolithic vertical cavity surface emitting lasers (VCSELs) on Si are demonstrated. The GaSb multi-quantum well active region embedded in an Al(Ga)Sb half-wave cavity spacer layer enables lasing under room-temperature optically-pumped conditions. The 13% lattice mismatch is accommodated by a spontaneously formed 2-D array of 90° misfit dislocations at the AlSb/Si interface. This growth mode produces very low defect density (∼8×105/cm2) and relaxed materials growth (98%) without the use of a buffer layer. Presented are VCSEL lasing spectra, light-in against light-out curves along with defect density measurements performed by microscopy and etch-pit density. A threshold excitation density of Ith=0.1 mJ/cm2 and a multimode lasing spectrum peaked at 1.62 µm, results from a 3 mm pump-spot size. [ABSTRACT FROM AUTHOR]