Gain Recovery in Heavily Irradiated Low Gain Avalanche Detectors by High Temperature Annealing

TL;DR

This study demonstrates that high-temperature annealing up to 450°C can significantly recover and improve the performance of heavily irradiated Low Gain Avalanche Detectors (LGADs), especially around 350°C.

Contribution

It provides new insights into the optimal annealing temperatures and durations for enhancing LGAD performance after neutron irradiation.

Findings

Annealing at 250°C for 5 minutes improves LGAD performance.

Maximum beneficial effect observed around 350°C in 30-minute isochronal annealing.

60-minute annealing at 350°C significantly increases V_gl, indicating defect reactivation.

Abstract

Studies of annealing at temperatures up to 450$^\circ$C with LGADs irradiated with neutrons are described. It was found that the performance of LGADs irradiated with 1.5e15 n/cm$^2$ was already improved at 5 minutes of annealing at 250$^\circ$C. Isochronal annealing for 30 minutes in 50$^\circ$C steps between 300$^\circ$C and 450$^\circ$C showed that the largest beneficial effect of annealing is at around 350$^\circ$C. Another set of devices was annealed for 60 minutes at 350$^\circ$C and this annealing significantly increased V$_{\mathrm{gl}}$. The effect is equivalent to reducing the effective acceptor removal constant by a factor of $\sim$ 4. Increase of V$_{\mathrm{gl}}$ is the consequence of increased effective space charge in the gain layer caused by formation of electrically active defects or re-activation of interstitial Boron atoms.