【作者】 李莉；

【导师】 陆启生；

【作者基本信息】 国防科学技术大学 ， 光学工程， 2010， 博士

【摘要】 随着光电探测器在军事和民用等诸多领域的广泛应用,半导体材料与半导体光电探测器的激光辐照效应越来越受到人们的重视。在实际应用中,光电探测器种类繁多,其光谱探测范围从紫外到可见光到远红外,然而每一种探测器都存在特定的光谱探测范围,即存在探测截止频率,我们把截止频率以内的光称为波段内光,超出截止频率的光称为波段外光。在光电对抗中,当干扰和毁伤用的激光为波段外光时,是否还能对光电探测器产生有效的干扰和毁伤,其作用机制如何,在目前国内外文献中还鲜有报道。本文从理论和实验两个方面较为系统的研究了波段外激光和双波段组合激光与半导体材料及光电探测器的相互作用机制,并探索研究了波段外激光对光电探测器的干扰和高效毁伤。对不同的光导型光电探测器进行了波段外激光辐照实验,发现了波段外激光辐照下探测器的电压响应方向与波段内正常探测的信号电压方向相反的响应规律。考虑到实际应用中,波段内信号光辐照是探测器的正常工作状态,激光干扰和毁伤通常在探测器的正常工作状态下进行,因此实验还系统研究了在波段内激光与波段外激光组合辐照下,探测器电压响应的信号输出。通过对大量实验数据的系统分析,得到双波段激光在不同功率密度组合的情况下,对探测器信号输出的影响规律,发现探测器对波段外激光辐照的电压响应也存在饱和效应,波段内背景激光辐照可以增大波段外激光的吸收系数,线性工作区间内的波段内背景光辐照可以增强波段外激光的信号干扰强度。对光伏型光电探测器进行了波段外激光辐照实验,得到光伏型光电探测器在不同功率密度波段外激光辐照下的动态响应规律。发现光伏型光电探测器对波段外激光的电压响应方向与波段内激光相同,但在开始和停止辐照瞬间,探测器的输出信号产生瞬间跳变,且该跳变方向随入射光功率密度不同而改变。发现了光伏型光电探测器内电动势产生的新的机制:在温度梯度存在的情况下,热激发自由载流子定向运动,在PN结区被结电场分离,在探测器两端分别累积正负电荷,形成电动势,我们把其命名为热生电动势。把热生电动势与光生电动势和温差电动势进行了对比分析,确定了热生电动势是PV型探测器在波段外激光辐照下电压响应的主要机制,在波段内激光辐照下热生电动势与光生电动势、温差电动势和Dember电动势共存,在端电压的信号输出中不能区分。利用双积分球-探测器系统,对半导体材料在波段内和波段外双光束组合激光辐照下的反射率和透射率进行了测量,得到了半导体材料与双波段组合激光的能量耦合规律。发现随波段内激光功率密度的增强,材料对于波段内激光的能量耦合效率降低;随波段外激光功率密度的增强,材料对波段外激光的能量耦合效率先降低后增大;波段内激光辐照可以增大材料对波段外激光的能量耦合效率。针对波段外激光辐照下光导型光电探测器的反向电压响应,提出了光激发热载流子输运的思想,并从玻耳兹曼方程出发,在取三阶矩的近似条件下,推导并建立了用于描述光激发热载流子输运的平衡能量流体动力学模型。并利用数值手段,自行编制了适用于描述不同探测器及不同功率密度组合激光辐照下载流子输运过程的计算程序。应用该程序对光导型HgCdTe光电探测器在双波段组合激光辐照下的载流子输运过程进行了数值模拟,结果与实验相吻合。利用该程序计算还得到了探测器在不同光功率密度以及不同激光辐照时间下探测器的破坏阈值。更多还原

【Abstract】 With the widespread use of photoelectric detectors in different domains, especially in military, more and more attentions are being paid to the irradiation effects of semiconductor materials and photoelectric detectors. The spectrum of the photoelectric detectors ranges from ultraviolet to far-infrared since there are plenty of semiconductor materials. However, as far as a specific detector is concerned, it can only responses to a specific band. We call the lights within the band“in-band lights”; otherwise we call them“out-of-band lights”. The scientific society knows well the irradiation effects of detectors by in-band lights, while there is little knowledge of the corresponding effects by out-of-band lights, which is also important in photoelectric countermeasure.This dissertation is focused on the mechanism of the interaction between in-band and out-of-band lasers and photoelectric semiconductor detectors via theoretical and experimental researches. Exploratory research is also made on the interference and efficient damage of out-of-band lasers on photodetectors.We carried out plenty of experiments in which different types of photoconductive (PC) detectors were irradiated by out-of-band lasers, finding that the voltage responses of detectors irradiated by out-of-band lasers were opposite to those by in-band lasers. We also studied the output of the detectors when irradiated by both in-band and out-of-band laser beams. Basing on the experimental results, we find the relationship between the output and the laser intensity. We conclude that a) there also exists saturation effect for the voltage response of PC detectors when irradiated by out-of-band lasers, b) in-band laser irradiation can increase the absorption of the out-of-band lasers, and c) in-band laser irradiation within linear-response domain can enhance the response of out-of-band lasers.We carried out experiments on photovoltage (PV) detectors irradiated by out-of-band lasers, and get the ruls of dynamic responses. We find that the voltage response of PV-type detector to out-of-band lasers is similar to that to in-band laser, while there were instantaneous jump for the voltage both at the beginning and at the end of laser irradiation. The direction of the voltage jump varied with laser intensity. Analysing the physical progress, we find new mechanics of voltage response, which we call thermovoltage. Comparing with photovoltage and thermopower, thermovoltage is the main mechanics of voltage response when out-of-band laser irradiating,and thermovoltage combines with photovoltage, thermopower and Dember voltage when in-band laser irradiating.Using double integrating sphere-photo detector system, we measured reflectance and transmittance for semiconductor materials under irradiation of both in-band and out-of-band lasers, getting the energy-coupling rules of semiconductor materials and lasers. We find that a) the energy-coupling coefficient of materials with in-band lasers decreases with in-band-laser power density increase; b) the coefficient for out-of-band lasers increases first and diminishes subsequently when the out-of-band laser power density increase; and c) irradiation of in-band lasers can increase the coupling coefficient for the out-of-band lasers.To explain the abnormal response of the PC-type detector for out-of-band lasers, we bring forward a concept of photoexcited hot carriers transportation. Basing on Boltzman formula, we obtain the energy balance hydrodynamic model under third-order approximation, which can describe the transportation of pohtoexcited hot carriers. Accordingly, we made a procedure that can describe different cases. Simulations for a PC-type HgCdTe detector irradiated by in-band and out-of-band lasers were done, agreeing well with experimental results. Basing on the procedure, we also have got the destruction threshold of detectors under different irradiating time and power.更多还原