The Effect of a Collector Ring on Low Gain Avalanche Detector for High Energy Physics Application

We proposed to design and fabricate a new Low Gain Avalanche Detector (LGAD) which can be used to replace the detector used in the high luminosity upgrade of the CERN Large Hadron Collider and synchrotron radiation detection. In this paper, we describe a 2x2 pads array Low Gain Avalanche Detector (LGAD) produced on epitaxial silicon with 33 mu m thickness on a 250 mu m thick support silicon wafer. The Low Gain Avalanche Detector (LGAD) has two guard rings. One is float guard ring (G-ring) without voltage which surrounds the whole 2x2 pads array, the other is collector ring (C-ring) surrounding each pad which has same voltage with active region. C-ring can reduce surface leakage current and the bulk current that can enhance signal to noise and radiation hardness. With C-ring biased, the data of the gain and responsivity were more accurate. The gain varied between 1 and 100 depending on the sensor bias voltage and responsivity was 4.9 A/W at 800nm when the gain was about 8. The time resolution was about 30ps at bias voltage of 220V.