Wide-field dynamic astronomy in the near-infrared with Palomar Gattini-IR and DREAMS

There have been a dramatic increase in the number of optical and radio transient surveys due to astronomical transients such as gravitational waves and gamma ray bursts, however, there have been a limited number of wide-field infrared surveys due to narrow field-of-view and high cost of infrared cameras, we present two new wide-field near-infrared fully automated surveyors; Palomar Gattini-IR and the Dynamic REd All-sky Monitoring Survey (DREAMS). Palomar Gattini-IR, a 25 square degree J-band imager that begun science operations at Palomar Observatory, USA in October 2018; we report on survey strategy as well as telescope and observatory operations and will also providing initial science results. DREAMS is a 3.75 square degree wide-field imager that is planned for Siding Spring Observatory, Australia; we report on the current optical and mechanical design and plans to achieve on-sky results in 2020. DREAMS is on-track to be one of the first astronomical telescopes to use an Indium Galium Arsenide (InGaAs) detector and we report initial on-sky testing results for the selected detector package. DREAMS is also well placed to take advantage and provide near-infrared follow-up of the LSST

Wide-field dynamic astronomy in the near-infrared with Palomar Gattini-IR and DREAMS

There have been a dramatic increase in the number of optical and radio transient surveys due to astronomical transients such as gravitational waves and gamma ray bursts, however, there have been a limited number of wide-field infrared surveys due to narrow field-of-view and high cost of infrared cameras, we present two new wide-field near-infrared fully automated surveyors; Palomar Gattini-IR and the Dynamic REd All-sky Monitoring Survey (DREAMS). Palomar Gattini-IR, a 25 square degree J-band imager that begun science operations at Palomar Observatory, USA in October 2018; we report on survey strategy as well as telescope and observatory operations and will also providing initial science results. DREAMS is a 3.75 square degree wide-field imager that is planned for Siding Spring Observatory, Australia; we report on the current optical and mechanical design and plans to achieve on-sky results in 2020. DREAMS is on-track to be one of the first astronomical telescopes to use an Indium Galium Arsenide (InGaAs) detector and we report initial on-sky testing results for the selected detector package. DREAMS is also well placed to take advantage and provide near-infrared follow-up of the LSST

Opening the dynamic infrared sky

While optical and radio transient surveys have enjoyed a renaissance over the past decade, the dynamic infrared sky remains virtually unexplored from the ground. The infrared is a powerful tool for probing transient events in dusty regions that have high optical extinction, and for detecting the coolest of stars that are bright only at these wavelengths. The fundamental roadblocks in studying the infrared time-domain have been the overwhelmingly bright sky background (250 times brighter than optical) and the narrow field-of-view of infrared cameras (largest is VISTA at 0.6 sq deg). To address these challenges, Palomar Gattini-IR is currently under construction at Palomar Observatory and we propose a further low risk, economical, and agile instrument to be located at Siding Spring Observatory, as well as further instruments which will be located at the high polar regions to take advantage of the low thermal sky emission, particularly in the 2.5 micron region

Evidence of Sub-Band Modulated Transport in Planar Fully Depleted Silicon-on-Insulator MOSFETs

International audienceModulation of the sub-band electron population in the inversion channel of 10-nm planar fully depleted silicon-on-insulator MOSFETs is evidenced by the bias dependence of inversion layer transport parameters. Two distinct inversion-layer electron species were detected by magnetic-field-dependent magnetoresistance measurements and high-resolution mobility spectrum analysis. According to self-consistent Poisson-Schrödinger calculations, these species correspond to carriers in distinct sub-bands within the Si channel region. The mobility peak of the carrier with the highest sheet density occurs under gate bias conditions that result in a minimum perpendicular effective electric field

Pt/GaN Schottky diode for propene (C3H6) gas sensing

Pt/GaN Schottky diode based gas sensors were fabricated and characterized for their sensitivity towards propene (C3H6) at high operating temperatures. The GaN epitaxial layer was deposited onto sapphire substrates by metal-organic chemical vapor deposition (MOCVD). Current-voltage (I-V) characteristics and the effective change in the barrier height of the sensors were investigated. The effective change of the barrier height was found to be 60.52 meV for 1% propene at 530°C. Dynamic response of the sensors at different propene concentrations in synthetic air was measured and a voltage shift of 231 mV and response time of 18s for 1% propene was obtained at temperatures as high as 530°C

Superlattice barrier HgCdTe nBn infrared photodetectors : validation of the effective mass approximation

Implementation of the unipolar barrier detector concept in HgCdTe-based compound semiconductor alloys is a challenging problem, primarily because practical lattice-matched materials that can be employed as the wide bandgap barrier layer in HgCdTe nBn structures present a significant valence band offset at the n-type/barrier interface, thus impeding the free flow of photogenerated minority carriers. However, it is possible to minimize the valence band offset by replacing the bulk HgCdTe alloy-based barrier with a CdTe-HgTe superlattice barrier structure. In this paper, an 8 × 8 k.p Hamiltonian combined with the nonequilibrium Green's function formalism has been employed to numerically demonstrate that the single-band effective mass approximation is an adequate numerical approach, which is valid for the modeling, design, and optimization of band alignment and carrier transport in HgCdTe-based nBn detectors incorporating a wide bandgap superlattice barrier.8 page(s

InAs light-to-heavy hole effective mass ratio determined experimentally from mobility spectrum analysis

Careful selection of the physical model of the material for a specific doping and selected operating temperatures is a non-trivial task. In numerical simulations that optimize practical devices such as detectors or lasers architecture, this challenge can be very difficult. However, even for such a well-known material as a 5 μm thick layer of indium arsenide on a semiinsulating gallium arsenide substrate, choosing a realistic set of band structure parameters for valence bands is remarkable. Here, the authors test the applicability range of various models of the valence band geometry, using a series of InAs samples with varying levels of p-type doping. Carefully prepared and pretested the van der Pauw geometry samples have been used for magneto-transport data acquisition in the 20-300 K temperature range and magnetic fields up to ±15 T, combined with a mobility spectra analysis. It was shown that in a degenerate statistic regime, temperature trends of mobility for heavy- and light-holes are uncorrelated. It has also been shown that parameters of the valence band effective masses with warping effect inclusion should be used for selected acceptor dopant levels and range of temperatures