1 Radiation Hardness of Monolithic Active Pixel Sensors Dennis Doering, Goethe-University Frankfurt am Main on behalf of the CBM-MVD-Collaboration Outline - Operation principle of MAPS - Radiation damage effects - MAPS with high-resistivity epitaxial layer - Parameters of radiation hardness - Conclusion

/17/21 Applications of MAPS Dennis Doering: Radiation hardness of MAPS DPG Mainz March Picture STAR Picture CBM International Linear Collider CBM-Experiment (FAIR, GSI) STAR-Experiment MAPS are developed for applications as vertex detector since 1999 at IPHC (Strasbourg).

/17/21 Operation principle Dennis Doering: Radiation hardness of MAPS DPG Mainz March SiO 2 N+ P+ P- P+ Sensing diode Epitaxial Layer P-Well Substrate N+ 50 µm ~50 µm thin sensors ⇒ low material budget High granularity ⇒ good spatial resolution µm => a few µm resolution

/17/21 Operation principle Dennis Doering: Radiation hardness of MAPS DPG Mainz March SiO 2 N+ P+ P- P+ Epitaxial Layer P-Well Substrate e- N+ e- Particle Sensing diode

/17/21 Non-ionizing radiation effects: Signal response Dennis Doering: Radiation hardness of MAPS DPG Mainz March SiO 2 N+P+ P- P+ Epitaxial Layer P-Well Substrate N+ e- Sensing diode Defects

/17/21 Signal response Dennis Doering: Radiation hardness of MAPS DPG Mainz March

/17/21 Non-ionizing radiation effects: Leakage current/Noise Dennis Doering: Radiation hardness of MAPS DPG Mainz March SiO 2 N+P+ P- P+ Epitaxial Layer P-Well Substrate N+ - - Sensing diode Defects

/17/21 Noise Dennis Doering: Radiation hardness of MAPS DPG Mainz March Radiation damage

/17/21 Noise Dennis Doering: Radiation hardness of MAPS DPG Mainz March Radiation damage

/17/21 Noise Dennis Doering: Radiation hardness of MAPS DPG Mainz March Radiation damage Cooling 2 times higher noise with respect to unirradiated

/17/21 Non-ionizing radiation effects Dennis Doering: Radiation hardness of MAPS DPG Mainz March SiO 2 N+P+ P- P+ Epitaxial Layer P-Well Substrate N+ e- - - Sensing diode Defects

/17/21 Non-ionizing radiation effects Dennis Doering: Radiation hardness of MAPS DPG Mainz March SiO 2 N+P+ P- P+ Epitaxial Layer P-Well Substrate N+ e- - - Radiation damage Sensing diode Defects

/17/21 Non-ionizing radiation effects Dennis Doering: Radiation hardness of MAPS DPG Mainz March SiO 2 N+P+ P- P+ Epitaxial Layer P-Well Substrate N+ e- - - Radiation damage Sensing diode Defects

/17/21 Signal to Noise ratio Dennis Doering: Radiation hardness of MAPS DPG Mainz March S/N limit (MIPS) Technical feasible limits reached: - Pixel pitch - Operating temperature Region of interest ?

/17/21 High-resistivity Dennis Doering: Radiation hardness of MAPS DPG Mainz March Larger depleted volumes ⇒ guided charge collection ⇒ Improved charge collection efficiency (CCE) SiO 2 N+P+ P- P+ Epitaxial Layer P-Well Substrate depleted volume Low-resistivity High-resistivity High-resistivity: Decrease of doping concentration in epitaxial layer. Sensing diode

/17/21 Signal response Dennis Doering: Radiation hardness of MAPS DPG Mainz March

/17/21 Signal response Dennis Doering: Radiation hardness of MAPS DPG Mainz March More charge collected in a high resistivity epitaxial layer.

/17/21 Signal response Dennis Doering: Radiation hardness of MAPS DPG Mainz March Radiation damage effect after 3·10 14 n eq /cm²: Some signal get lost due to recombinations. However, the high resistivity sensor is even irradiated better than the low resistivity sensor unirradiated.

/17/21 Improvements using high resistivity Dennis Doering: Radiation hardness of MAPS DPG Mainz March Error bars: Signal fit uncertainty * 10% noise uncertainty *Beam test is pending S/N limit (MIPS) * Parameters: - Pixel pitch - Operating temperature - Resistivity of epitaxial layer

/17/21 How to improve the non-ionizing radiation hardness of MAPS: -Operate the sensor at low temperature ( -30°C) -Small pixel pitch ( 10µm) -High-resistivity epitaxial layer (used here 400 Ωcm) Conclusion Dennis Doering: Radiation hardness of MAPS DPG Mainz March

/17/21 How to improve the non-ionizing radiation hardness of MAPS: -Operate the sensor at low temperature ( -30°C) -Small pixel pitch ( 10µm) -High-resistivity epitaxial layer (used here 400 Ωcm) ⇒ Radiation hardness beyond 3·10 14 n eq /cm² Conclusion Dennis Doering: Radiation hardness of MAPS DPG Mainz March