Extreme ultraviolet detection using AlGaN-on-Si inverted Schottky photodiodes

We report on the fabrication of aluminum gallium nitride (AlGaN) Schottky diodes for extreme ultraviolet (EUV) detection. AlGaN layers were grown on silicon wafers by molecular beam epitaxy with the conventional and inverted Schottky structure, where the undoped, active layer was grown before or after the n-doped layer, respectively. Different current mechanisms were observed in the two structures. The inverted Schottky diode was designed for the optimized backside sensitivity in the hybrid imagers. A cut-off wavelength of 280 nm was observed with three orders of magnitude intrinsic rejection ratio of the visible radiation. Furthermore, the inverted structure was characterized using a EUV source based on helium discharge and an open electrode design was used to improve the sensitivity. The characteristic He I and He II emission lines were observed at the wavelengths of 58.4 nm and 30.4 nm, respectively, proving the feasibility of using the inverted layer stack for EUV detectio

Development of a photon-counting near-fano-limited x-ray CMOS image sensor for THESEUS' SXI

THESEUS (Transient High Energy Sky & Early Universe Surveyor) is one of the three candidates for the M5 mission of the European Space Agency. The favoured mission will be announced in 2021 for an expected launch in 2032. THESEUS will be equipped with a Soft X-ray Imager (SXI) composed of a set of two telescopes using micro-pore optics offering an overall field of view of 0.5 sr (<2' accuracy) for X-ray energies between 300 eV and 5 keV. The focal plane of each SXI telescope has a 16 x 16 cm² cooled detector area. However, the limited radiator accommodation on the spacecraft prohibits the use of CCDs since cooling the focal planes to an optimal temperature for radiation hardness (<-100 °C) is not feasible. Therefore, the development of a suitable CMOS Image Sensor (CIS), capable of handling the expected levels of radiation at higher operating temperatures (approximately -30 °C) has been proposed. To demonstrate the performance required for the THESEUS SXI detector, a 2 x 2 cm² prototype is under development using Open University pixel designs in a Teledyne-e2v digital CMOS platform. The pixel design will allow full depletion over silicon thickness of 35 µm for optimal soft X-ray quantum efficiency and instrument background suppression, and will be capable of near-Fano-limited spectral resolution that will also be of prime interest for synchrotron and Free Electron Lasers (FEL) applications. In this paper, we will present the design considerations and simulations leading to the implemented structures complying with THESEUS' SXI requirements

High density integrated optoelectronic circuits for high speed photonic microsystems

High-density hybrid integration of III-V compound optoelectronics (OE) with Complementary Metal Oxide Semiconductor (CMOS) Integrated Circuits (ICs) is emerging as a technology able to provide the features and performance required by the next generation of high functionality information processing subsystems. The aim of this PhD thesis is the study of hybrid integration technologies of lll-V OEs with CMOS of high speed photonic microsystems under the view of developing not only a heterogeneous integration technology but also a compact and efficient full model for a special type laser device, the VCSEL (Vertical Cavity Surface Emitting Laser). Regarding hybrid integration, in this work a SiO₂/SOG (Spin-On-Glass) based and a metallic bonding technique are proposed which can be used for the bonding of the photonic wafer on the CMOS wafer. Definition of the procedure and identification of critical steps are taking place and finally implementation of an in-plane optical link is demonstrated. Concerning metallic bonding, appropriate metal alloy’s composition and structure, lithography and alloy patterning possibility and electrical characteristics are investigated. This thesis also studies the possibility for accurate simulation of the mixed photonic/VLSI modules under a unified VLSI design CAD environment through the presentation of a model for the VCSEL device. Implementation of the model (fundamental device rate equations, thermal effects, non-linear gain and transparency number functions and input parasitics elements) is accomplished. Simulation results are compared with commercial available laser measurements and a three-step parameter extraction procedure is developed. To conclude, the purpose of the work presented in this thesis is to obtain an understanding of hybrid optoelectronic microsystems since (a) in a technological level, proposes an hybrid integration technology of lll-V OEs with CMOS and (b) in a device level approach, studies in deep and develops a model, of great value for the IC designers, for a basic photonic module of the full high-speed photonic microsystem.Η τεχνολογία της υψηλής πυκνότητας υβριδικής ολοκλήρωσης οπτικοηλεκτρονικών III-V κυκλωμάτων (ΟΕ) με CMOS Ολοκληρωμένα Κυκλώματα (IC’s) διαφαίνεται ικανή στο να παρέχει τα χαρακτηριστικά και τις επιδόσεις που απαιτούνται από τα υψηλών προδιαγραφών υποσυστήματα επεξεργασίας πληροφοριών νέας γενιάς. Στόχος αυτής της διδακτορικής διατριβής είναι η μελέτη των υψίρυθμων φωτονικών μικροσυστημάτων τόσο από τη σκοπιά της ανάπτυξης συγκεκριμένης τεχνολογίας για την υβριδική ολοκλήρωση τους όσο και από την πλευρά της ανάπτυξης ενός πλήρους μοντέλου για ένα συγκεκριμένου τύπου οπτικοηλεκτρονικό στοιχείο φωτοεκπομπής, το VCSEL (Vertical Cavity Surface Emitting Laser). Όσον αφορά την υβριδική ολοκλήρωση μελετώνται τεχνικές συγκόλλησης δισκιδίων τόσο με τη χρήση SiO₂ και Spin-on-Glass (SOG) όσο και με την χρήση κράματος μετάλλων. Αναφορικά, παρουσιάζεται η μεθοδολογία που αναπτύχθηκε για τη συγκόλληση με χρήση SOG, καθορίζονται τα κρίσιμα στάδια, χαρακτηρίζονται τα κολλημένα δισκίδια και σχεδιάζεται και κατασκευάζεται μια ολοκληρωμένη οπτοηλεκτρονική διασύνδεση. Παρόμοια, σχετικά με τη μεταλλική συγκόλληση, καθορίζεται η δομή και η σύσταση του κράματος, μελετάται η ομοιομορφία των επιμεταλλώσεων, μετρώνται ηλεκτρικές παράμετροι, και μελετάται η δυνατότητα μορφοποίησης του κράματος. Παράλληλα, η διδακτορική διατριβή ασχολείται με την εισαγωγή μέσα σε ενιαίο περιβάλλον σχεδιασμού ολοκληρωμένων κυκλωμάτων πολύ μεγάλης κλίμακας (VLSI) ενός πλήρους μοντέλου για τα VCSELS. Το πλήρες μοντέλο, το οποίο περιλαμβάνει το παρασιτικό κύκλωμα εισόδου, τα εσωτερικά θερμο-ηλεκτρικά χαρακτηριστικά του στοιχείου και τις φυσικές διαφορικές εξισώσεις παραγωγής φωτός, υλοποιείται, προσομοιώνεται και σε συνδυασμό με τις πειραματικές μετρήσεις εμπορικών λέιζερ εκτιμάται η εγκυρότητα και η πληρότητά του ενώ ταυτόχρονα αναπτύσσεται μεθοδολογία εξαγωγής των παραμέτρων του μοντέλου

A CMOS image sensor for soft x-ray astronomy

A monolithic CMOS image sensor based on the pinned photodiode (PPD) and optimized for X-ray imaging in the 300 eV to 5 keV energy range is described. Featuring 40 µm square pixels and 40 µm thick, high resistivity epitaxial silicon, the sensor is fully depleted by reverse substrate bias. Backside illumination (BSI) processing has been used to achieve high X-ray QE, and a dedicated pixel design has been developed for low image lag and high conversion gain. The sensor, called CIS221-X, is manufactured in a 180 nm CMOS process and has three different 512×128-pixel arrays on 40 µm pitch, as well as a 2048×512 array of 10 µm pixels. CIS221-X also features per-column 12-bit ADCs, digital readout via four high-speed LVDS outputs, and can be read out at 45 frames per second. CIS221-X achieves readout noise of 2.6 e- RMS and full width at half maximum (FWHM) at the Mn-Kα 5.9 keV characteristic X-ray line of 153 eV at -40 °C. This paper presents the characterization results of the first backside illuminated CIS221-X, including X-ray response and readout noise. The newly developed sensor and the technology underpinning it is intended for diverse applications, including X-ray astronomy, synchrotron, and X-ray free electron laser light sources

CHIEM: A New Compact Camera for Hyperspectral Imaging

We have developed an engineering model of a novel compact hyperspectral imager. The CHIEM instrument is designed to be compatible with a 12U CubeSat satellite, offering a swath of 100km and a GSD of 25m from 600km altitude. The hyperspectral sensor has thin film interference filters directly deposited on a 12Mpixel CMOS 2D detector array. The spectral range covers 470 to 900 nm, with narrow spectral resolution (FWHM) between 5 and 10nm. Besides the hyperspectral zone which covers 2/3 of the detector array, it also contains 2 panchromatic zones without filters. While the baseline design uses a conventional front-side illuminated CMOS sensor, the development also includes filter depositions on a back-side illumination (BSI) version with a higher sensitivity. For the optical design of the front telescope, CHIEM uses a very compact three mirror anastigmat, which allows a wide field of view in both across track and along track direction (\u3e 9.5o x 7.2o). The readout electronics (ROE) provides all required sensor interfaces (power, control, data) enabling its full performance operation, and also a set of backend interfaces for system power, remote control, and backend remote data (to EGSE) and local storage interfaces

European laser development for LISA

We present the European development of an engineering model Laser Head for LISA. This single box includes a seed laser, an electro-optical phase modulator, a fiber amplifier and all PCBs to operate the Laser Head