Diamond (C*) is a wide bandgap semiconductor (Bandgap energy of 5.5 eV, i.e. 220 nm at room temperature), which makes the sensors ‘solar-blind’: insensitive to the solar spectrum below the Earth atmosphere (at sea level) with a good UV/visible response ratio.
Diamond exhibits several superior properties in comparison to silicon. It has a high charge carrier mobility at room temperature with large breakdown electric field, a low dielectric constant (i.e. low capacitance) and low intrinsic carrier density that makes cooling for noise reduction unnecessary. Its dense tetrahedral structure and stable covalent sp3 bonding between Carbon atoms explain the good radiation hardness of diamond detectors.
- LYRA PIN diamond detector
- LYRA MSM diamond photodetectors
The launch in November 2009, of the European Space Agency Project for On-Board Autonomy 2 (ESA-PROBA2) technological mission has given us the unique opportunity to test detectors based on diamond materials for the first time in a solar space mission. LYRA (http://proba2.oma.be/data/LYRA) is a solar EUV-VUV radiometer onboard the PROBA2 micro satellite. LYRA benefits from wide bandgap detectors based on diamond: it is the first space assessment of the pioneering BOLD detector development program. Diamond makes the sensors radiation-hard and solar-blind: its large bandgap energy makes them quasi-insensitive to visible light.
- LYRA overview
- PROBA2 microsatellite (courtesy of ESA)