Study of gain homogeneity and radiation effects of Low Gain Avalanche Pad Detectors

Abstract

a b s t r a c tSilicon detectors with intrinsic charge amplification implementing a n ++ -p + -p structure are considered as a sensor technology for future tracking and timing applications in high energy physics experiments. The performance of the intrinsic gain in Low Gain Avalanche Detectors (LGAD) after irradiation is crucial for the characterization of radiation hardness and timing properties in this technology.LGAD devices irradiated with reactor neutrons or 800 MeV protons reaching fluences of 2.3 × 10 16 n eq /cm 2 were characterized using Transient Current Technique (TCT) measurements with red and infra-red laser pulses. Leakage current variations observed in different production lots and within wafers were investigated using Thermally Stimulated Current (TSC). Results showed that the intrinsic charge amplification is reduced with increasing fluence up to 10 15 n eq /cm 2 which is related to an effective acceptor removal. Further relevant issues were charge collection homogeneity across the detector surface and leakage current performance before and after irradiation.

Displacement Damage in Silicon Detectors for High Energy Physics

“…Based on this fact, the advantage of the increased signal of the LGAD device is expected to give an advantage over conventional detectors for small cell volumes and fast shaping times [123] and in particular for complex detector systems such as pixel sensors with other significant noise sources. Also, the multiplication layer in LGAD is impacted by a displacement damage leading to a significant degradation in the gain with increasing fast hadron fluence reaching a complete loss of gain at a fast-charged particle fluence of about 5 × 10 14 cm −2 and leaving only little gain after exposure to neutron fluences of 2 × 10 15 cm −2 [123], [124].…”

Analysis of the performance of low gain avalanche diodes for future particle detectors

“…Gains are typically in the range of 5-100, which is adequate to compensate for the limited number of signal electrons generated by Minimum Ionizing Particles (MIPs) in a thinner-than-usual (300 μm) active volume. As in the scheme depicted in figure 1, the n-type implant typically has a shallow profile that extends a few hundreds of nanometers from the interface, whereas the p − type gain layer is typically implanted deeper into the substrate with peak doping concentrations of order 10 16 / 10 17 cm −3 [4][5][6][7][8][9][10][11][29][30][31][32][33][34]. The majority of the signal is produced by the movement of multiplied holes toward the back of the sensor.…”

“…In a typical set-up, a trigger sensor with known timing characteristics is aligned with the Device Under Test (DUT) and a radioactive 𝛽-source (typically 90Sr, which emits electrons with energies of 0.546 MeV and 2.28 MeV) as indicated in figure 11. Typical betas used in the lab have enough energy to be good approximation of MIPs for the first detector only, while they lose more energy in the second device [1,5,7,8,12,21,23,29,33,35,37,40]. Characterizations at various temperatures was also possible by moving the whole setup inside a cold box.…”

Stochastic theory of charge dynamics and recombination in defect clusters in bulk silicon

“…The HE particles generate not only mobile charges (electrons and holes). High energies of incoming particles yield various types of lattice point defects, which shorten the device lifetime and the detectors degrade [2,3]. The avalanche-like defect generation of vacancies and interstitial atoms has been proposed [4].…”