Annealing effects on operation of thin Low Gain Avalanche Detectors

Abstract

Several thin Low Gain Avalanche Detectors from Hamamatsu Photonics were irradiated with neutrons to different equivalent fluences up to Φ eq = 3 • 10 15 cm −2 . After the irradiation they were annealed at 60 • C in steps to times > 20000 minutes. Their properties, mainly full depletion voltage, gain layer depletion voltage, generation and leakage current, as well as their performance in terms of collected charge and time resolution, were determined between the steps. It was found that the effect of annealing on timing resolution and collected charge is not very large and mainly occurs within the first few tens of minutes. It is a consequence of active initial acceptor concentration decrease in the gain layer with time, where changes of around 10% were observed. For any relevant annealing times for detector operation the changes of effective doping concentration in the bulk negligibly influences the performance of the device, due to their small thickness and required high bias voltage operation. At very long annealing times the increase of the effective doping concentration in the bulk leads to a significant increase of the electric field in the gain layer and, by that, to the increase of gain at given voltage. The leakage current decreases in accordance with generation current annealing.

Bistability of the BiOi complex and its implications on evaluating the “acceptor removal” process in p-type silicon

“…High Voltage CMOS sensors) [6,7]. Radiation effects in these devices were surveyed mainly at macroscopic level, by monitoring their electrical performance after irradiation with different particles of various fluence levels and the changes during annealing at moderate temperatures (60, 80 °C) [8][9][10][11]. The latter is important for planning running scenarios as well as for quantitatively predicting the effects of the annealing on operation if unplanned events occur.…”

Determination of impact ionization parameters for low gain avalanche detectors produced by HPK

“…However, it has been shown that the bulk only impacts the performance of irradiated sensors when either no annealing has occured or at very long annealing times. When the bulk concentration is at a minimum, which is at around the standard annealing time of 80 minutes at 60 • C, the bulk gain is negligible [21].…”

Hadron damage investigation of low gain avalanche detectors

“…After annealing, the leakage current decreased by ⇠30%, and the breakdown voltage increased by ⇠20 V. There was no significant change in + fd or + gl due to the annealing. While studies of annealing in neutron-irradiated sensors have been performed, similar studies for proton irradiated devices are not extensively reported in the literature [8,9]. Accordingly, some irradiated wafers from both HPK and FBK have been set aside unannealed, and a comprehensive study of annealing after proton irradiations is underway.…”