Silicon avalanche photodiodes (Si APD) in linear mode operation have been used in spaceborne lidars around Mars, Mercury, Earth, and the Moon over the past 25 years. We have been monitoring the space radiation damages to some of these Si APDs over their mission lifetimes. It was found that the Si APD performance degradation depended on the location of the Si APDs inside the lidars and the thickness of the shielding materials around them. The major accumulated radiation effect was found to be the increase of the dark currents. Most of the radiation damage remained after weeks of annealing at room temperature. Heating the devices at high temperature could anneal the radiation damage to certain extent. Recently, the lidar on the Global Ecosystem Dynamics Investigation (GEDI) mission captured many individual pulse waveforms from transient radiation events from the Si APDs. We subsequently conducted a single event effects (SEE) test of a GEDI Engineering Model Si APD using 64 MeV protons to reproduce the anomalous pulse waveforms observed from GEDI in orbit. In this paper, we will present a summary of the Si APD performance monitored from several space lidars developed by and operated at NASA Goddard Space Flight Center. We will also present the laboratory test data from the recent SEE tests.
The structure of a silicon avalanche photodiode (APD) has a significant impact on the probability of light creating charge carriers and on the generated noise due to the multiplication process or excess noise factor (ENF). In this paper, we will review front-illuminated and back-illuminated APD structures and their impact on ENF as a function of wavelength from 400 nm to 1000 nm for recently commercially produced silicon APDs targeting LIDAR and other applications. The experimental setup developed for characterization will be described and highlight the differences between the studied structures. APDs with different junction profiles were produced and measurement of ENF was found to match McIntyre’s theory for experimental k-factors (ratio of the hole impact ionization rate to that of electrons) ranging from approximately 0.05 to 0.008. The generated illuminated noise as a function of responsivity can be used as a guideline to select the APD achieving the best signal-to-noise ratio (SNR) for a given application. To help meeting this condition, optimizing the electrical field profile of an APD and making certain the electrons are the primary carriers initiating the avalanche is critical.
Silicon Avalanche Photodiodes (APDs) are used in NASA’s Global Ecosystem Dynamics Investigation (GEDI) that was launched in December 2018 and is currently measuring the Earth’s vegetation vertical structure from the International Space Station. The APDs were specially made for space lidar with a much lower hole-to-electron ionization coefficient ratio (k-factor ~0.008) than that of commercially available silicon APDs in order to reduce the APD excess noise. A silicon heater resistor was used under the APD chip to heat the device to 70°C to improve its quantum efficiency at the 1064-nm laser wavelength while maintaining a low dark current such that the overall signal to noise ratio is optimized. Special APD protection circuits were included to raise the overload damage threshold to prevent device damage from strong laser returns from specular surfaces, such as still water bodies, and space radiation events. The APD and a hybrid transimpedance amplifier circuit were hermetically sealed in a TO-8 type metal package with a sufficiently low leak rate to ensure a multi-year operation lifetime in space. The detector assemblies underwent a series of pre-launch tests per NASA Goddard Environmental Verification Standard for space qualification. The APDs have performed exactly as expected in space. A detailed description of the GEDI detector design, signal and test results are presented in this paper.
Silicon photomultipliers with high photon detection efficiency in the 350 to 800 nm range and low dark count rate are currently being developed in a variety of geometry, microcell size and area in order to address the needs of the analytical, life science, medical imaging community as well as for various scientific and technological applications. This SiPM development platform is based on previous knowledge of low dark count avalanche photodiode operated in Geiger-mode found in the Excelitas single photon counting module. Low dark counts and low temperature sensitivity are especially important when tiling up SiPMs to form larger area detectors such as block detectors typically used in positron emission tomography. The latest developments include; 1. Optical trenches to suppress crosstalk which allowed to increase the operating voltage range from 5 to 10 V above breakdown, 2. Tailored parasitic capacitance to obtain single photon timing resolution close to 200 ps FWHM and 3. Improved PDE at shorter wavelengths by optimizing the entrance window. A corrected energy resolution of 12.0 % was typically obtained at 511 keV which, alongside the good timing resolution, makes this SiPM a perfect candidate for time-of-flight PET and other application requiring a timing resolution better than 200 ps.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.