A variety of silicon carbide (SiC) detectors have been developed to study their sensitivity, incl... more A variety of silicon carbide (SiC) detectors have been developed to study their sensitivity, including Schottky photodiodes, p-i-n photodiodes, avalanche photodiodes (APDs), and single photon-counting APDs. Due to the very wide bandgap and thus extremely low leakage current, SiC photo-detectors show excellent sensitivity. The specific detectivity, D*, of SiC photodiodes are many orders of magnitude higher than the D* of other solid state detectors, and for the first time, comparable to that of photomultiplier tubes (PMTs). SiC APDs have also been fabricated to pursue the ultimate sensitivity. By operating the SiC APDs at a linear mode gain over 106, single photoncounting avalanche photodiodes (SPADs) in UV have been demonstrated.
ABSTRACT The invention concerns a single detector with two designable wavelengths and bandwidths ... more ABSTRACT The invention concerns a single detector with two designable wavelengths and bandwidths for ultraviolet detection based on n-/n+ GaN and AlGaN structures grown over sapphire substrates.
2007 International Semiconductor Device Research Symposium, 2007
Summary form only given. We report on the design, fabrication and testing of a back-illuminated, ... more Summary form only given. We report on the design, fabrication and testing of a back-illuminated, voltage bias selectable, dual band deep ultraviolet (UV) AlGaN photodetector for integration into space spectroscopic instrumentation. The photodetector can separate UV-A and UV-B band radiation by bias switching a two terminal n-p-n homojunction structure that is fabricated in the same pixel. When a forward bias
We describe efforts to develop a robust fabrication technology for making submillimeter detectors... more We describe efforts to develop a robust fabrication technology for making submillimeter detectors integrated with single electron transistors as readout amplifiers. This work will make a fundamental and critical contribution to the development of new classes of imaging detector arrays with photon-counting sensitivity in the submillimeter, and intrinisic energy resolution in the UV/optical and x-ray.
We are developing superconducting direct detectors for submillimeter astronomy that can detect in... more We are developing superconducting direct detectors for submillimeter astronomy that can detect individual photons. These Al-based STJ detectors count quasiparticles generated breaking Cooper-pairs by photon absorption in the submillimeter band. They could yield high quantum efficiency, microsecond response time, and sensitivities of le-20 W/rt(Hz). The use of antenna coupling to a small absorber also suggests the potential for novel instrument designs and scalability to imaging or spectroscopic arrays. The use of an RF readout scheme also naturally lends itself to wavelength-division multiplexing for simultaneous readout of large arrays. We describe device concept, fabrication and dark current characterization of these detectors. Measurements of the STJ dark current scale exponentially with temperature down to 200 mK and can be as small as 1 fA, corresponding to detector sensitivity less than le-20 W/rt(Hz). We are also developing hot-electron microbolometers that can be used as cal...
INTRODUCTION: Several types of superconducting detectors are being developed for NASA application... more INTRODUCTION: Several types of superconducting detectors are being developed for NASA applications, including transition edge sensors (TES)1, superconducting tunnel junctions (STJ)2, and photon-counting direct detectors (SQPC)3. Despite the complexity of cryogenic operation, such detectors are desirable because of capabilities such as single-photon spectroscopy, or extreme levels of sensitivity, which cannot be obtained with uncooled detectors. Large format detector arrays will be facilitated by sensitive, fast, compact, low-power, multiplexable, on-chip amplifiers. For high impedance detectors such as the STJ and SQPC, the Radio Frequency Single Electron Transistor (RF-SET) seems to be an ideal readout amplifier.
We report on our progress towards the development of arrays of X-ray microcalorimeters as candida... more We report on our progress towards the development of arrays of X-ray microcalorimeters as candidates for the high resolution x-ray spectrometer on the Constellation-X mission. The microcalorimeter arrays (30 x 30) with appropriate pixel sizes (0.25 mm. x 0.25 mm) and high packing fractions (greater than 96%) are being developed. Each individual pixel has a 10 micron thick Bi X-ray absorber that is shaped like a mushroom to increase the packing fraction, and a Mo/Au proximity effect superconducting transition edge sensor (TES). These are deposited on a 0.25 or 0.5 micron thick silicon nitride membrane with slits to provide a controllable weak thermal link to the sink temperature. Studies are underway to model, test and optimize the TES pixel uniformity, critical current, heat capacity and the membrane thermal conductance in the array structure. Fabrication issues and procedures, and results of our efforts based on these optimizations will be provided.
We present the key technologies and capabilities that will enable a future, large-aperture ultrav... more We present the key technologies and capabilities that will enable a future, large-aperture ultravioletopticalinfrared (UVOIR) space observatory. These include starlight suppression systems, vibration isolation and control systems, lightweight mirror segments, detector systems, and mirror coatings. These capabilities will provide major advances over current and near-future observatories for sensitivity, angular resolution, and starlight suppression. The goals adopted in our study for the starlight suppression system are 10-10 contrast with an inner working angle of 40 milliarcsec and broad bandpass. We estimate that a vibration and isolation control system that achieves a total system vibration isolation of 140 dB for a vibration-isolated mass of 5000 kg is required to achieve the high wavefront error stability needed for exoplanet coronagraphy. Technology challenges for lightweight mirror segments include diffraction-limited optical quality and high wavefront error stability as well...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
... [17] Integrated Detector and Electronics, AS, http://www.ideas.no. [18] LM Barbier, F Birsa, ... more ... [17] Integrated Detector and Electronics, AS, http://www.ideas.no. [18] LM Barbier, F Birsa, J Odom, SD Barthelmy, N Gehrels, JF Krizmanic, D Palmer, AM Parsons, CM Stahle and J Tueller. IEEE Trans. Nucl. Sci-NS, 46 1 (1999), p. 7. ...
Page 1. ANTENNA-COUPLED SUPERCONDUCTING TUNNEL JUNCTIONS WITH SINGLE-ELECTRON TRANSISTOR READOUT ... more Page 1. ANTENNA-COUPLED SUPERCONDUCTING TUNNEL JUNCTIONS WITH SINGLE-ELECTRON TRANSISTOR READOUT FOR DETECTION OF SUB-MM RADIATION Thomas R. Stevenson,1 Wen-Ting Hsieh,1,4 Mary ...
This talk will discuss recent dark current measurements of single quasiparticle photon detectors.... more This talk will discuss recent dark current measurements of single quasiparticle photon detectors. The detector uses small superconducting Josephson junctions to convert incoming submillimeter photons into quasiparticles, which are then measured as a current. Unfortunately, there will be a non-zero current, the dark current, even in the absence of photons. It is this dark current that should ultimately limit the sensitivity of the device. One unavoidable contribution to the dark current is the thermally excited quasiparticles. By characterizing the temperature dependence of the dark current, we have seen that it arises solely from thermally excited quasiparticles and continues to decrease exponentially with temperature, just as BCS theory predicts, down to 260 mK. In order to observe this BCS behavior, it was necessary to suppress sub-gap structure arising from the AC Josephson effect. By applying a magnetic field to the devices, this structure was reduced to a few percent of its initial value. Overall, these are very promising results that already predict that a shot-noise limited detector using similar junctions would have an NEP of 8x10-20 W/&surd;Hz.
A variety of silicon carbide (SiC) detectors have been developed to study their sensitivity, incl... more A variety of silicon carbide (SiC) detectors have been developed to study their sensitivity, including Schottky photodiodes, p-i-n photodiodes, avalanche photodiodes (APDs), and single photon-counting APDs. Due to the very wide bandgap and thus extremely low leakage current, SiC photo-detectors show excellent sensitivity. The specific detectivity, D*, of SiC photodiodes are many orders of magnitude higher than the D* of other solid state detectors, and for the first time, comparable to that of photomultiplier tubes (PMTs). SiC APDs have also been fabricated to pursue the ultimate sensitivity. By operating the SiC APDs at a linear mode gain over 106, single photoncounting avalanche photodiodes (SPADs) in UV have been demonstrated.
ABSTRACT The invention concerns a single detector with two designable wavelengths and bandwidths ... more ABSTRACT The invention concerns a single detector with two designable wavelengths and bandwidths for ultraviolet detection based on n-/n+ GaN and AlGaN structures grown over sapphire substrates.
2007 International Semiconductor Device Research Symposium, 2007
Summary form only given. We report on the design, fabrication and testing of a back-illuminated, ... more Summary form only given. We report on the design, fabrication and testing of a back-illuminated, voltage bias selectable, dual band deep ultraviolet (UV) AlGaN photodetector for integration into space spectroscopic instrumentation. The photodetector can separate UV-A and UV-B band radiation by bias switching a two terminal n-p-n homojunction structure that is fabricated in the same pixel. When a forward bias
We describe efforts to develop a robust fabrication technology for making submillimeter detectors... more We describe efforts to develop a robust fabrication technology for making submillimeter detectors integrated with single electron transistors as readout amplifiers. This work will make a fundamental and critical contribution to the development of new classes of imaging detector arrays with photon-counting sensitivity in the submillimeter, and intrinisic energy resolution in the UV/optical and x-ray.
We are developing superconducting direct detectors for submillimeter astronomy that can detect in... more We are developing superconducting direct detectors for submillimeter astronomy that can detect individual photons. These Al-based STJ detectors count quasiparticles generated breaking Cooper-pairs by photon absorption in the submillimeter band. They could yield high quantum efficiency, microsecond response time, and sensitivities of le-20 W/rt(Hz). The use of antenna coupling to a small absorber also suggests the potential for novel instrument designs and scalability to imaging or spectroscopic arrays. The use of an RF readout scheme also naturally lends itself to wavelength-division multiplexing for simultaneous readout of large arrays. We describe device concept, fabrication and dark current characterization of these detectors. Measurements of the STJ dark current scale exponentially with temperature down to 200 mK and can be as small as 1 fA, corresponding to detector sensitivity less than le-20 W/rt(Hz). We are also developing hot-electron microbolometers that can be used as cal...
INTRODUCTION: Several types of superconducting detectors are being developed for NASA application... more INTRODUCTION: Several types of superconducting detectors are being developed for NASA applications, including transition edge sensors (TES)1, superconducting tunnel junctions (STJ)2, and photon-counting direct detectors (SQPC)3. Despite the complexity of cryogenic operation, such detectors are desirable because of capabilities such as single-photon spectroscopy, or extreme levels of sensitivity, which cannot be obtained with uncooled detectors. Large format detector arrays will be facilitated by sensitive, fast, compact, low-power, multiplexable, on-chip amplifiers. For high impedance detectors such as the STJ and SQPC, the Radio Frequency Single Electron Transistor (RF-SET) seems to be an ideal readout amplifier.
We report on our progress towards the development of arrays of X-ray microcalorimeters as candida... more We report on our progress towards the development of arrays of X-ray microcalorimeters as candidates for the high resolution x-ray spectrometer on the Constellation-X mission. The microcalorimeter arrays (30 x 30) with appropriate pixel sizes (0.25 mm. x 0.25 mm) and high packing fractions (greater than 96%) are being developed. Each individual pixel has a 10 micron thick Bi X-ray absorber that is shaped like a mushroom to increase the packing fraction, and a Mo/Au proximity effect superconducting transition edge sensor (TES). These are deposited on a 0.25 or 0.5 micron thick silicon nitride membrane with slits to provide a controllable weak thermal link to the sink temperature. Studies are underway to model, test and optimize the TES pixel uniformity, critical current, heat capacity and the membrane thermal conductance in the array structure. Fabrication issues and procedures, and results of our efforts based on these optimizations will be provided.
We present the key technologies and capabilities that will enable a future, large-aperture ultrav... more We present the key technologies and capabilities that will enable a future, large-aperture ultravioletopticalinfrared (UVOIR) space observatory. These include starlight suppression systems, vibration isolation and control systems, lightweight mirror segments, detector systems, and mirror coatings. These capabilities will provide major advances over current and near-future observatories for sensitivity, angular resolution, and starlight suppression. The goals adopted in our study for the starlight suppression system are 10-10 contrast with an inner working angle of 40 milliarcsec and broad bandpass. We estimate that a vibration and isolation control system that achieves a total system vibration isolation of 140 dB for a vibration-isolated mass of 5000 kg is required to achieve the high wavefront error stability needed for exoplanet coronagraphy. Technology challenges for lightweight mirror segments include diffraction-limited optical quality and high wavefront error stability as well...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
... [17] Integrated Detector and Electronics, AS, http://www.ideas.no. [18] LM Barbier, F Birsa, ... more ... [17] Integrated Detector and Electronics, AS, http://www.ideas.no. [18] LM Barbier, F Birsa, J Odom, SD Barthelmy, N Gehrels, JF Krizmanic, D Palmer, AM Parsons, CM Stahle and J Tueller. IEEE Trans. Nucl. Sci-NS, 46 1 (1999), p. 7. ...
Page 1. ANTENNA-COUPLED SUPERCONDUCTING TUNNEL JUNCTIONS WITH SINGLE-ELECTRON TRANSISTOR READOUT ... more Page 1. ANTENNA-COUPLED SUPERCONDUCTING TUNNEL JUNCTIONS WITH SINGLE-ELECTRON TRANSISTOR READOUT FOR DETECTION OF SUB-MM RADIATION Thomas R. Stevenson,1 Wen-Ting Hsieh,1,4 Mary ...
This talk will discuss recent dark current measurements of single quasiparticle photon detectors.... more This talk will discuss recent dark current measurements of single quasiparticle photon detectors. The detector uses small superconducting Josephson junctions to convert incoming submillimeter photons into quasiparticles, which are then measured as a current. Unfortunately, there will be a non-zero current, the dark current, even in the absence of photons. It is this dark current that should ultimately limit the sensitivity of the device. One unavoidable contribution to the dark current is the thermally excited quasiparticles. By characterizing the temperature dependence of the dark current, we have seen that it arises solely from thermally excited quasiparticles and continues to decrease exponentially with temperature, just as BCS theory predicts, down to 260 mK. In order to observe this BCS behavior, it was necessary to suppress sub-gap structure arising from the AC Josephson effect. By applying a magnetic field to the devices, this structure was reduced to a few percent of its initial value. Overall, these are very promising results that already predict that a shot-noise limited detector using similar junctions would have an NEP of 8x10-20 W/&surd;Hz.
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Papers by Carl Stahle