毫秒脉冲激光致硅光电二极管电学损伤的有限元分析及实验研究

Finite element analysis and experimental study on electrical damage of silicon photodiode induced by millisecond pulse laser

为了研究毫秒脉冲激光致硅基PIN光电二极管电学损伤,基于热传导及弹塑性力学理论,在光电二极管内部材料各向同性并且P-I-N三层结构之间满足温度连续和热流平衡条件下,建立毫秒脉冲激光辐照硅基PIN光电二极管二维轴对称模型,采用有限元方法模拟分析了1064 nm Nd:YAG毫秒量级脉冲激光辐照硅基PIN光电二极管的温度场与应力场分布,并实验测量了硅基PIN光电二极管实验前后的电学参数.结果表明,激光辐照硅基PIN光电二极管时,温升使材料表面熔融、烧蚀,并且在空间上存在温度梯度变化,即激光辐照产生的热与应力使光敏面及硅晶格晶键损伤,最终造成光电探测器的探测性能下降.研究结果可为毫秒脉冲激光辐照硅基PIN光电二极管电学损伤机理奠定基础.

In this paper, based on the thermal elasto-plastic constitutive theory and the equivalent specific heat method, the electrical damage in the silicon-based positive-intrinsic-negative （PIN） photodiode irradiated by millisecond （ms）-pulsed laser is investigated. On condition that the internal material of the photodiode is isotropic and threelayer structure of the P-I-N satisfying temperature continuity and heat flow balance, a two-dimensional （2D） simulation axisymmetric model for silicon-based PIN photodiode irradiated by ms-pulsed laser is built. The thermal and stress field distribution are simulated in the silicon-based PIN photodiode irradiated by the Nd：YAG ms-pulsed laser at 1064 nm through using the finite element simulation software. At the same time, electrical parameters before and after the experiment of the silicon-based PIN photodiode irradiated by pulsed laser are measured. The experimental results show that the surface is melted and ablated gradually with the increase of temperature in the high energy pulsed laser, and there is a gradient change for the temperature in spatial distribution. With the increase of laser energy density, photoelectric detector shows the temperature rise phenomenon and damage effect is more obvious. When the tensile stress or compressive stress is greater than 1.7 GPa, the photosensitive surface and the silicon lattice are damaged with the changes of thermal and stress fields. Bond cleavage can change the photogenerated carrier transport channel, and the transport time can be longer. In this process, the photogenerated electron-hole pairs are readily recombined, carrier lifetime decrease and carrier concentration increase, which leads to the increase of the dark current and the decrease of the responsivity. Eventually the performance of photodetector detection is reduced. Through comprehensive comparison between experiment and simulation, one can confirm that this theoretical model has a considerable level of reliability. The conclusion we can draw is that the threshold of electrical damage is 1.7 GPa. So the control of annealing temperature is extremely important for the process of making PIN photodiode. Preventing the lattice damage of the material can improve the product yield rate. In addition, from the point of view of the use of products, the stability of the working environment can extend the service life of products, and the detection accuracy is guaranteed. Conclusively, the results in this paper establish the foundation to investigate the electrical damage mechanism in the silicon-based PIN photodiode irradiated by ms-pulsed laser.