Carrier localization and in-situ annealing effect on quaternary Ga1-xInxAsySb1-y/GaAs quantum wells grown by Sb pre-deposition

Using temperature-dependent photoluminescence spectroscopy, we have investigated and compared intrinsic InGaAs, intrinsic GaInAsSb, and p-i-n junction GaInAsSb quantum wells (QWs) embedded in GaAs barriers. Strong carrier localization inside the intrinsic GaInAsSb/GaAs QW has been observed together with its decrease inside the p-i-n sample. This is attributed to the effect of an in-situ annealing during the top p-doped AlGaAs layer growth at an elevated temperature of 580 degrees C, leading to Sb-atom diffusion and even atomic redistribution. High-resolution X-ray diffraction measurements and the decrease of both maximum localization energy and full delocalization temperature in the p-i-n QW sample further corroborated this conclusion. (C) 2013 American Institute of Physics. (http://dx.doi.org/10.1063/1.4795866

Electro-optical and lasing properties of hybrid quantum dot/quantum well material system for reconfigurable photonic devices

We characterize the electro-optical and lasing properties of a hybrid material consisting of multiple InAs quantum dot (QD) layers together with an InGaAs quantum well (QW) grown on a GaAs substrate. Over 40 nm Stark shift of the InGaAs QW leading to 9 dB extinction ratio was demonstrated. Lasing operation at the QD first excited state transition of 1070 nm was achieved and together with < 10 ps absorption recovery the system shows promise for high-speed mode-locked lasers and electro-modulated lasers. (C) 2013 American Institute of Physics. (http://dx.doi.org/10.1063/1.4791565

Optical properties of hybrid quantum dot/quantum well active region based on GaAs system

We experimentally investigate the optical properties of a novel hybrid material/structure consisting of a GaInNAs quantum well and stacked InAs/InGaAs quantum dot layers on GaAs substrate. We demonstrate that the strong quantum confined Stark effect within the quantum well can effectively control well-dot detuning when reverse bias voltage is applied. With a combination of low-and room-temperature time resolved luminescence spectra we infer device absorption recovery time under 30 ps. These properties could be utilized in high-speed optoelectronics devices, in particular electro-absorption modulated lasers and reconfigurable multisection devices, where the hybrid quantum dots - quantum well material system could offer easily and rapidly interchangeable function, i.e., emission gain or variable attenuation, of each section depending on the external bias. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4752279

Electro-optic properties of GaInAsSb/GaAs quantum well for high-speed integrated optoelectronic devices

The electro-optic properties of strained GaInAsSb/GaAs quantum wells (QWs) are investigated. A single QW p-i-n sample was grown by molecular beam epitaxy with antimony (Sb) pre-deposition technique. We numerically predict and experimentally verify a strong quantum confined Stark shift of 40 nm. We also predict a fast absorption recovery times crucial of high-speed optoelectronic devices mainly due to strong electron tunneling and thermionic emission. Predicted recovery times are corroborated by bias and temperature dependent time-resolved photoluminescence measurements indicating (<= 30 ps) recovery times. This makes GaInAsSb QW an attractive material particularly for electroabsorption modulators and saturable absorbers. (C) 2013 American Institute of Physics. (http://dx.doi.org/10.1063/1.4775371

Orally bioavailable isothioureas block function of the chemokine receptor CXCR4 in vitro and in vivo.

The interaction of the chemokine receptor CXCR4 with its ligand CXCL12 is involved in many biological processes such as hematopoesis, migration of immune cells, as well as in cancer metastasis. CXCR4 also mediates the infection of T-cells with X4-tropic HIV functioning as a coreceptor for the viral envelope protein gp120. Here, we describe highly potent, selective CXCR4 inhibitors that block CXCR4/CXCL12 interactions in vitro and in vivo as well as the infection of target cells by X4-tropic HIV

Special ergolines efficiently inhibit the chemokine receptor CXCR3 in blood

The structure activity relationship of highly potent special ergolines which selectively block the chemokine receptor CXCR3 is reported. The most potent compounds showed IC50 values below 10 nM in both ligand binding and Ca2+-mobilization assays. However, these compounds were poorly active in an assay that measures receptor occupancy in blood. Introduction of polar substituents led to derivatives with IC50 values below 10 nM in this assay. Among them was compound 11a which showed both a favorable PK profile and cross reactivity with rodent CXCR3 making it a promising tool compound to further explore the role of CXCR3 in animal models