Impact of charge trapping on the energy resolution of Ge detectors for rare-event physics searches
Impact of charge trapping on the energy resolution of Ge detectors for rare-event physics searches
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DOI：
10.1088/1361-6471/ab9796
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发表时间：
2019-09
期刊：
影响因子：
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通讯作者：
D. Mei;Mukund Bharadwaj;W.-Z. Wei;R. Panth;Jing Liu;H. Mei;Yangyang Li;P. Acharya;S. Bhattarai;K. Kooi;M. Raut;Xiansong Sun;Alex Kirkvold;Kunming Dong;Xianghua Meng;Guojian Wang;Gang Yang
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文献类型：
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作者：
D. Mei;Mukund Bharadwaj;W.-Z. Wei;R. Panth;Jing Liu;H. Mei;Yangyang Li;P. Acharya;S. Bhattarai;K. Kooi;M. Raut;Xiansong Sun;Alex Kirkvold;Kunming Dong;Xianghua Meng;Guojian Wang;Gang Yang
电荷俘获降低了锗探测器的能量分辨率，这要求在寻找暗物质和无中微子双β衰变时具有更高的实验灵敏度。我们调查的电荷捕获过程中，利用九个平面探测器制造的超声波生长的晶体与众所周知的净杂质水平。根据Shockley-Ramo定理导出了电荷收集效率与电荷俘获长度的函数关系。此外，我们开发了一个模型，相关的能量分辨率与电荷收集效率。然后将该模型应用于实验数据。结果，电荷收集效率和电荷捕获长度相应地被确定。利用Lax模型（进一步发展的CDMS合作者），绝对杂质水平确定的9个检测器。这些参数的知识，当结合其他性状，如Fano因子作为一个可靠的指标，晶体内的电荷捕获的固有性质。我们表明，电子捕获是更严重的比空穴捕获在p型探测器和电荷收集效率取决于绝对杂质水平的Ge晶体时，适当的偏置电压施加到检测器。当收集电子的绝对杂质能级小于1.0 × 10 $^{11}/$cm$^{3}$，收集空穴的绝对杂质能级小于2.0 × 10 $^{11}/$cm$^{3}$时，发现电荷俘获可忽略不计。
Charge trapping degrades the energy resolution of germanium (Ge) detectors, which require to have increased experimental sensitivity in searching for dark matter and neutrinoless double-beta decay. We investigate the charge trapping processes utilizing nine planar detectors fabricated from USD-grown crystals with well-known net impurity levels. The charge collection efficiency as a function of charge trapping length is derived from the Shockley-Ramo theorem. Furthermore, we develop a model that correlates the energy resolution with the charge collection efficiency. This model is then applied to the experimental data. As a result, charge collection efficiency and charge trapping length are determined accordingly. Utilizing the Lax model (further developed by CDMS collaborators), the absolute impurity levels are determined for nine detectors. The knowledge of these parameters when combined with other traits such as the Fano factor serve as a reliable indicator of the intrinsic nature of charge trapping within the crystals. We demonstrate that electron trapping is more severe than hole trapping in a p-type detector and the charge collection efficiency depends on the absolute impurity level of the Ge crystal when an adequate bias voltage is applied to the detector. Negligible charge trapping is found when the absolute impurity level is less than 1.0$\times$10$^{11}/$cm$^{3}$ for collecting electrons and 2.0$\times$10$^{11}/$cm$^{3}$ for collecting holes.