Study On Charge Collection Properties Of New 3D-Trench Electrode Si Detector

Semiconductor detectors, with excellent performances of fast response, high sensitivity, ease of integration, etc., have been the priority detectors in photons and high-energy particle detection, and they are widely used in aerospace, medical test, high-energy physics experiment and other fields. For the detectors applied in high-energy physics experiment, for example the large hadron collision(LHC) experiment in Europe, they suffer from a very high radiation fluence, which lead to severe degradations in detector performance, such as the increasing of the leakage current, high resistivity, etc.. In recent years, with increasing of radiation fluence on high-energy experiment, say SLHC, radiation fluence has reached up to 1×1016 neq/cm2,which will keep increasing in the future. Such high radiation will cause defect effects seriously, and the trapping of free carriers by defect levels becomes the main limiting factor. Scientists have been trying to improve radiation hardness of detector,one effective way is to design a detector with novel configuration, which has high charge collection rate and small depletion voltage. Recently, a new structure detector named 3D-trench electrode detector was designed, which has a uniform electric field and low depletion voltage, and its performance is much better than the traditional 3D detector with column electrodes only. The research and development test for this kind detector is being performed. 3D-trench electrode detector will replace traditional column 3D detector in the future, and it will be widely used in high-energy physics experiment, X-ray detection and other areas.Charge collection performance, as one of the important parameters of detectors, plays a crucial role in efficiency and precision of high-energy particles detection or X-ray detection. Charge collection properties on this new 3D-trench detector have not been studied in our country or at abroad, yet, especially for the charge collection properties at very high radiation environment. In this paper, we analyzed radiation effects in silicon caused by high radiation environment, including changes of space charge concentration, the life time of minority carrier, and trapping of free carries by defect level, etc., then using the Ramo Theorem, we obtain the charge collection model in 3D-trench electrode detector. Meanwhile we use the device simulation software(Silvaco TCAD) to simulate the electric field and weighting field of 3D-trench electrode detector, finally we obtain the charge collection properties of 3D-trench detector in detail. The results for charge collection of 3D-trench detector show that:(1) For the non-irradiated detector, the total collected charge doesn’t change with the particle incident position.(2) For the irradiated detector, the total collected charge changes with the particle incident position.(3) The collected charge reduces with the increasing radiation fluence.(4) Enhancing bias voltage will increase the collected charge, and the collected charge will tend to a saturation value finally.(5) Shorting the electrodes spacing will increase the total collected charge obviously. And also we estimate the average collected charge by a single particle at a random position. The calculation method of charge collection is very novel, and it can also be applied to the charge collection model of other devices. The results in this paper will provide some insight into the application of high-energy experiment and nuclear physics experiment in the future.