Optimization of fabrication processes of the mesa-type GaAs:Te blocked-impurity-band detector
In this work, the device structure of the mesa-type GaAs:Te blocked-impurity-band detector was designed. The fabrication processes were presented briefly, and optimization of the fabrication processes was investigated. A 3-micron-thick SiO2 film was deposited as resist to substitute for photoresist in the 50-micron-deep mesa etching process. In addition, a bi-layer photoresist lithography technique was adopted to optimize the process of electrode fabrication. It is demonstrated that the device quality can be improved significantly after optimization.
Design consideration of GaAs-based blocked-impurity-band detector with the absorbing layer formed by ion implantation
Drawbacks and problems of the traditional liquid-phase-epitaxy grown mesa GaAs-based blocked-impurity-band (BIB) detector are discussed. In order to improve device performance, a novel planar GaAs-based BIB detector with the absorbing layer formed by ion implantation is proposed and modeled. Physical models and key parameters used for simulation are presented. Our results reveal that the transition region between the absorbing layer and the blocking layer can be as narrow as 3.125 $$\mu \hbox {m}$$μm by adopting the novel design. Bias-dependent electric field characteristics are then obtained by taking into account the immaturity of GaAs-based material. Temperature-dependent dark current characteristics are also simulated to investigate the impurity-band effect. Finally, the dependences of dark current and photoresponse on the thickness of the blocking layer are studied. It is demonstrated that the effective dark current suppression and sufficient photoresponse level can be realized by a proper control over the thickness of the blocking layer.
CALISTO: the Cryogenic Aperture Large Infrared Space Telescope Observatory
CALISTO, the Cryogenic Aperture Large Infrared Space Telescope Observatory, will enable extraordinarily high sensitivity far-infrared continuum and moderate (R ~ 1000) resolution spectroscopic observations at wavelengths from ~30µm to ~300 μm - the wavelengths between those accessible by JWST and future ground based facilities. CALISTO's observations will provide vital information about a wide range of important astronomical questions including (1) the first stars and initial heavy element production in the universe; (2) structures in the universe traced by H2 emission; (3) the evolution of galaxies and the star formation within them (4) the formation of planetary systems through observations of protostellar and debris disks; (5) the outermost portions of our solar system through observations of Trans-Neptunian Objects (TNOs) and the Oort cloud. With optics cooled to below 5 K, the photon fluctuations from the astronomical background (Zodiacal, Galactic, and extragalactic) exceed those from the telescope. Detectors with a noise equivalent power below that set by the background will make possible astronomical-background-limited sensitivity through the submillimeter/far-infrared region. CALISTO builds on studies for the SAFIR (Single Aperture Far Infrared) telescope mission, employing a 4m x 6m off-axis Gregorian telescope which has a simple deployment using an Atlas V launch vehicle. The unblocked telescope with a cold stop has minimal sidelobes and scattering. The clean beam will allow astronomical background limited observations over a large fraction of the sky, which is what is required to achieve CALISTO's exciting science goals. The maximum angular resolution varies from 1.2" at 30 µm to 12" at 300 μm. The 5σ 1 hr detectable fluxes are ▵S(dν/ν = 1.0) = 2.2x10-20 Wm-2, and ▵S(dν/ν = 0.001) = 6.2x10-22 Wm-2. The 8 beams per source confusion limit at 70 μm is estimated to be 5 μJy. We discuss CALISTO optics, performance, instrument complement, and mission design, and give an overview of key science goals and required technology development to enable this promising far IR/submm mission.