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Abstract: Vertical-cavity surface-emitting lasers are attractive light sources particularly for gas-sensing applications. Using the AlGaInAs/InP material system, an emission wavelength ranges from 1.3 to 2.05μm has already been achieved [G. Boehm, M. Ortsiefer R. Shau, J. Rosskopf, C. Lauer, M. Maute, F. Köhler, F. Mederer, R. Meyer, M.-C. Amann, in: Proceedings of MBE XII, J. Crystal Growth (2002) pp. 748–753]. Within this range, absorption lines of gases like H2S (1590nm), CH4 (1654nm), H2O (1877nm) and CO2 (2004nm) are detectable [G. Totschnig, M. Lackner, R. Shau, M. Ortsiefer, J. Rosskopf, M.-C. Amann, F. Winter, Meas. Sci. Technol. 14 (2003) 472]. The aim of this work is a further expansion of the emission wavelength up to 2.3μm, exploiting the well-known InP-based material system and the fabrication technique of buried tunnel junction (BTJ) VCSELs [R. Shau, M. Ortsiefer, J. Rosskopf, G. Boehm, C. Lauer, M. Maute, M.-C. Amann, in: Proceedings of SPIE, 5364 (2004) 1–15] to reach the technologically important absorption lines of carbon monoxide (CO) around 2.33μm. [Copyright &y& Elsevier]

The Amazon forests act as a global reserve for carbon, have very high biodiversity, and provide a variety of additional ecosystem services. These forests are, however, under increasing pressure, coming mainly from deforestation, despite the fact that accurate satellite monitoring is in place that produces annual deforestation maps and timely alerts. Here, we present a proof of concept for rapid deforestation monitoring that engages the global community directly in the monitoring process via crowdsourcing while subsequently leveraging the power of deep learning. Offering no tangible incentives, we were able to sustain participation from more than 5500 active contributors from 96 different nations over a 6-month period, resulting in the crowd classification of 43,108 satellite images (representing around 390,000 km2). Training a suite of AI models with results from the crowd, we achieved an accuracy greater than 90% in detecting new and existing deforestation. These findings demonstrate the potential of a crowd–AI approach to rapidly detect and validate deforestation events. Our method directly engages a large, enthusiastic, and increasingly digital global community who wish to participate in the stewardship of the global environment. Coupled with existing monitoring systems, this approach could offer an additional means of verification, increasing confidence in global deforestation monitoring. [ABSTRACT FROM AUTHOR]

In this Letter, the thermal stability of GaInAsSb grown by molecular-beam epitaxy was investigated. We found a strong blueshift for both bulk material and multiple-quantum-well (MQW) structures caused by thermal annealing. The shift is almost independent of design parameters such as indium concentration, strain, and growth parameters such as temperature. For a 500-nm-thick GaInAsSb bulk layer, a blueshift of 83 meV was found after annealing for 2 h at 520 °C, whereas for MQW structures the maximum shift was 61 meV. [ABSTRACT FROM AUTHOR]

A tunnel junction for intradevice contacts on GaSb substrates has been realized. By using solid source molecular beam epitaxy, we have fabricated abrupt, heavily doped homo- and heterojunctions of InAssSbd and GaSb to form a low resistive ohmic tunnel junction. The resitivity achieved was as low as 2.6310-5 Ω cm2. [ABSTRACT FROM AUTHOR]

A series of wet-chemical etchants for materials lattice-matched to GaSb was investigated. The etch rates for GaSb, AlAsSb, InAsSb and InAs with etch solutions based on KNa–tartaric acid (C4H4KNaO6), citric acid (C6H8O7) and hydrochloric acid were determined and the selectivities for the four different etching solutions are shown. The applicability of the selectivity between GaSb and InAs (respectively InAsSb) with C4H4KNaO6:HCl: H2O2:H2O (selectivity higher than 15:1) and C6H8O7:H2O2 (selectivity around 1:100) is proved by a substrate removal experiment. Also a new etchant for AlAsSb is proposed: HCl:H2O2:H2O etches AlAsSb versus GaSb with a selectivity of 5:1 and the GaSb surface underneath is smooth and without any remaining particles of oxidized aluminium. [ABSTRACT FROM AUTHOR]

A study of the optical properties of a set of InAsxSb1-x/Al0.15In0.85As0.77Sb0.23/GaSb multiple quantum wells (0.82