We developed a numerical solver for the drift–diffusion and Poisson equations in one-dimensional semiconductor detectors, including the possibility of an arbitrary number of donors and acceptors acting as trapping centers, Schottky or Ohmic contact type, velocity saturation at high electric fields, and external illumination. The temporal evolution of the system is computed by solving the full set of coupled differential equations self-consistently at each time step. An adaptive algorithm dynamically adjusts the time step allowing one to accurately track dynamics occurring at any relevant time scale within acceptable computational times. We investigated the case of semi-insulating, Cr-compensated GaAs sensors under illumination of monochromatic x-ray, showing the behavior of all the main quantities with special focus on the phenomenon of polarization, i.e., the space charge accumulation leading to the collapse of the electric field and signal loss. The model predictions are in agreement with experimental count rate efficiency data obtained with a 500 μm-thick GaAs:Cr sensor, readout by an IBEX photon counting application-specific integrated circuit (ASIC) with a pixel size of 75 µm and illuminated with 55 keV x-ray over a wide range of impinging fluxes. Finally, we investigated the maximum sustainable flux for the same detector type illuminated with monochromatic x-ray in the range 10–60 keV.

中文翻译：

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半绝缘、铬补偿 GaAs 像素化传感器在高 X 射线通量下的偏振动力学模拟

我们为一维半导体探测器中的漂移扩散方程和泊松方程开发了一种数值求解器，包括任意数量的施主和受主充当俘获中心的可能性、肖特基或欧姆接触类型、高电场下的速度饱和以及外部照明。系统的时间演化是通过在每个时间步自洽地求解全套耦合微分方程来计算的。自适应算法动态调整时间步长，允许人们在可接受的计算时间内准确跟踪在任何相关时间尺度上发生的动态。我们研究了在单色 X 射线照射下的半绝缘、铬补偿 GaAs 传感器的情况，显示所有主要量的行为，特别关注极化现象，即导致电场崩溃和信号损失的空间电荷积累。模型预测与用 500 μm 厚的 GaAs:Cr 传感器获得的实验计数率效率数据一致，由 IBEX 光子计数专用集成电路 (ASIC) 读取，像素尺寸为 75 μm，用 55 keV 照明X 射线在宽范围的撞击通量上。最后，我们研究了用 10-60 keV 范围内的单色 X 射线照射的相同探测器类型的最大可持续通量。模型预测与用 500 μm 厚的 GaAs:Cr 传感器获得的实验计数率效率数据一致，由 IBEX 光子计数专用集成电路 (ASIC) 读取，像素尺寸为 75 μm，用 55 keV 照明X 射线在很宽的撞击通量范围内。最后，我们研究了用 10-60 keV 范围内的单色 X 射线照射的相同探测器类型的最大可持续通量。模型预测与用 500 μm 厚的 GaAs:Cr 传感器获得的实验计数率效率数据一致，由 IBEX 光子计数专用集成电路 (ASIC) 读取，像素尺寸为 75 μm，用 55 keV 照明X 射线在很宽的撞击通量范围内。最后，我们研究了用 10-60 keV 范围内的单色 X 射线照射的相同探测器类型的最大可持续通量。