4T-PPD-APS光子辐射响应特性分析

Analysis of Photon Radiation Response Characteristics of 4T-PPD-APS

分析了含有4个晶体管的钳位光电二极管有源像素传感器(4T-PPD-APS)的结构特点以及γ射线光子在像元内的能量沉积过程。通过建立传感器像元及像素阵列仿真计算模型,并结合γ射线辐射响应实验,对有源像素传感器(APS)在不同光子能量及不同放射性水平条件下的响应特性进行了研究。研究结果表明:γ光子在光电二极管空间电荷区内沉积能量并形成扩散光电流是APS发生光子响应现象的根本原因;像素值的平均值随剂量率的增大呈先增大后趋于饱和的趋势;当典型事件区域内出现多个峰值时,像素值的统计值不能准确反映辐射场放射性水平。

The structural features and the energy deposition process ofγ-ray photons in the pixels for the 4 transistors pinned photodiode active pixel sensors（4 T-PPD-APSs）are analyzed.By the establishment of simulation calculation models of sensor pixels and pixel array and by the experiment ofγ-ray radiation response,the response characteristics of the active pixel sensors（APS）under different photon energies and different radioactivity level conditions are investigated.The research results show that,the energy deposition of theγphoton at the photodiode spatial charge area and the formation of diffused photocurrent are the root causes for the photon response phenomena occurring in the APS.The mean pixel value first increases and then tends to saturate with the increase of the dose rate.When the multiple peaks appear in the typical event areas,the statistical pixel value cannot accurately reflect the radioactivity level of the radiation fields.