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低能电子束非电离能损(NIEL)的研究
于新
学位类型硕士
导师何承发
2012-05-01
学位授予单位中国科学院研究生院
学位授予地点北京
学位专业微电子学与固体电子学
关键词Niel 位移损伤效应 林哈德因子 P-i-n光电二极管 Led
摘要本文研究了半导体材料的非电离能损(NIEL)和半导体器件的位移损伤效应。位移损伤的度量指标为位移损伤剂量(DDD),即非电离能损(NIEL)与粒子注量的乘积。欲得半导体器件的位移损伤响应与DDD的关系,需研究半导体材料的NIEL和半导体器件参数变化与粒子注量的关系。 首先计算了电子入射硅、锗、砷化镓材料的经典NIEL。经典NIEL值在高能区域与器件参数有良好的线性关系,但在低能区域呈现二次关系。其原因是低能区域位移损伤的微观机制是复杂的多体问题,基于二体碰撞近似(BCA)的经典NIEL模型并不适用。故借助分子动力学(MD)模拟的结果,阐明低能区域复杂的位移损伤产生机制,并用其更精确的位移原子个数来修正经典NIEL,得出在最新模型和数据下的0~200MeV电子的NIEL值,及缺陷数量、林哈德因子和微分散射截面等信息。 随后用1.8MeV的电子、60Coγ辐照p-i-n光电二极管和LED,测得p-i-n光电二极管在不同辐照偏置下的辐照响应,观察到正偏辐照会引起注入退火的现象。通过测量p-i-n光电二极管的I-V曲线、LED的光强找到了位移损伤的敏感参数,即p-i-n光电二极管的在正向脉冲电流下的电压值、反向偏压下的暗电流值和LED的发光强度,并得到了这些敏感参数在电子注量为1E14 e/cm2~1E17 e/cm2范围内随电子注量的变化规律。从I-V特性上得出位移损伤产生的缺陷在正向偏置的p-i-n光电二极管中起到俘获载流子的作用,在反向偏置时起到产生载流子的作用。从C-V特性得出缺陷具有补偿载流子的作用。LED的光电流衰减表明了位移损伤引入的缺陷使LED的非辐射复合作用增强,从而降低了LED的发光效率。在光谱中发现了红移现象,通过分析追溯到电阻率在辐照条件下变大是光谱红移的首因。此外在高注量电子辐照条件下,光谱中大于峰值波长的区域产生了新的峰值,说明产生的缺陷参与了辐射复合的过程。 通过比较p-i-n光电二极管在60Coγ与电子辐照的敏感参数变化,即正向脉冲电流下的电压值、反向偏压下的暗电流值与电子注量的关系,可看出p-i-n光电二极管对电离损伤不敏感,且60Coγ不能造成明显的位移损伤,故其参数退化是由位移损伤引起的。并建立了位移损伤敏感参数与位移损伤剂量(DDD)的关系。
其他摘要The non-ionizing energy loss (NIEL) of semiconducting materials and displacement damage effects are studied. Displacement damage dose (DDD), the product of NIEL and particle fluence, is the metrics for displacement damage effects. In order to build the relationship between displacement damage response and DDD, semiconducting materials’ NIEL and the function of device parameters’ variation and partical fluence must be studied. The NIEL for electrons on Si, Ge and GaAs, ranges from 100keV to 200MeV, are calculated via classical NIEL model. Due to binary cascade approximation (BCA), the classical NIEL model failed to describe displacement damage mechanism accurately at low incident energy for some particles such as electrons. In order to predict the amount of displacement damage accurately, more complex processes at low incident energy region are interpreted using molecular dynamics (MD) simulation results. The classical NIEL is modified by MD’s displacements amount, the threshold energy in MD calculation, Mott cross section, and energy partition function are also discussed. LED and p-i-n photodiode are irradiate1E14 e/cm2 to 1E17 e/cm2. I-V d by 1.8MeV electron beam and 60Coγ subsequently. The displacement damage response for p-i-n photodiode in different irradiated bias are measured, which indicate injection annealing occurs under forward irradiated bias. I-V characteristic of p-i-n photodiode, such as the voltage under forward pluse current, dark current under reverse voltage, and LED’s light intensity are sensitive to electron fluence and 60Coγ. The variation relationships between these sensitive parameters and electron fluence are measured from characteristic of p-i-n photodiode also reveal that defects induced by displacement damage play the role of trapping centre with forward current, while play the role of generation centre with reverse voltage. And C-V characteristic of p-i-n photodiode demonstrate that defects compensate both donors and acceptors. LED’s light currrent reduction with electron illustrate that defects enhance nonradiative recombination, which reduce the LED’s luminous efficiency. LED’s Spectrum redshift imply that resistivity become higher after radiation. New spectral values appear in the right hand of peak wave value illustrate that defects participate in radiative recombination. The p-i-n photodiode’s sensitive parameters are compared between 60Coγ and electron beam, which clarify that p-i-n photodiode is not sensitive to ionization damage caused by 60Coγ, and 60Coγ can not induce significient displacement damage to p-i-n photodiode. Therefore, displacement damage is the reason of sensitive parameters’ degeneration. The relationships between sensitive parameters’ degeneration and DDD are builded.
文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4374
专题材料物理与化学研究室
作者单位中国科学院新疆理化技术研究所
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于新. 低能电子束非电离能损(NIEL)的研究[D]. 北京. 中国科学院研究生院,2012.
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