https://indico.ihep.ac.cn//event/9864/

Yuzhen has presented the JC-104 Paper “Technology developments and first measurements of Low Gain Avalanche Detectors (LGAD) for high energy physics applications”.

The talk had started with the introduction:

A new concept of silicon radiation detector with intrinsic multiplication of the charge, called Low Gain Avalanche Detector (LGAD). Difference between APD (Avalanche Photo Diode) and LGAD: low gain requested to detect high energy particles the possibility to have fine segmentation pitches thinner devices with the same output signal

Simulation: effect on geometry of electrodes, structure, doping

Measurement:

I-V, C-V of sensor for wafer uniformity

charge collection measurement irradiation/non-irradiation

effect of temperature and anneal

She has shown the Schematic diagram of the LGAD sensor. She showed the simualted effect on Boron Implant Dose by the graph. There was a graph on Structure of JTE and Field plate (See figure on Page-5). The measurements of the voltage capability beyond 1100V has been shown in Fig-6 and Fig-7 showed 1/c^2-V curves for a sampling of the fabricated devices. Each curve corresponds to similar samples located on the same wafer with boron implant dose=1.6*10^13/cm^2. Fig-8 showed the charge collection measurement for the collected charge and noise signal for two LGAD samples after Sr-90 source MIPs exposure. The comparison is with the response of a conventional non-multipying pad diode(2328-10). Fig-9 was showing the effect of temperature dependence of the multiplication factor. Charge collection response for a MIP has been measured at different operational temperatures. The expected signal for a standard 300mm-thick detector has been depicted with a dashed line to allow the comparison with a non-multiplying detector. The annealing effect has been shown in Fig-10 and Fig-11.

Questions:

Yuhang’s Question: In this paper :”The measurements were performed on the same device after subjecting it to progressively increasing neutron fluences. Before each measurement, the sample underwent 80 min annealing at 60 ℃.” In general, annealing reduces defects, why should they anneal and then measure after irradiation?

Answers: In my opinion, the annealing will partially recover the effect of irradiation.

Xin’s question: On the last page of the paper, why “The p+ concentration is affected (reduced) by irradiation” ? Answer: The irradiation will remove the implanted acceptors of the p+ section at the junction.

Ryuta’s Question: Here is my question on this paper: At page 4, a simple explanation on the temperature dependence of the gain is described as “ … since the impact ionization coefficients exhibit temperature dependence, becoming larger as the temperature is reduced [14]” I only have heard about this effect, but I do not know why it is? Could you find/give further explanation ? (of course, I could check the reference[14] or something else by myself but …)

Answer: We cna check the paper in the reference[TEMPERATURE DEPENDENCE OF AVALANCHE MULTIPLICATION IN SEMICONDUCTORS] for this explanation.

Ryuta has shown the abstract and the motivation for the next JC-105 Paper, “Measurement of tt normalised multi-differential cross sections in pp collisions t √s = 13 TeV, and simultaneous determination of the strong coupling strength, top quark pole mass, and parton distribution functions”.