基于热刺激电流的空间电介质载流子迁移率测量方法

为了研究空间用聚酰亚胺材料在不同温度下的载流子迁移率,提出了基于热刺激电流(TSC)测量载流子迁移率的模型。对试样施加一段时间的电压,会有电荷注入到材料中。当试样温度降低到液氮温度时,注入电荷被保持在材料的陷阱中。假设入陷的电荷服从玻尔兹曼分布,陷阱中电荷会随着材料温度的上升而出陷,然后在自建电场的作用下向电极传输。在这个物理模型的基础上,推导出了载流子迁移率的解析公式。通过计算,得到了聚酰亚胺在不同温度下的载流子迁移率。同时,采用空间电荷限制电流方法测量了聚酰亚胺材料的迁移率。通过比较2种方法得到的迁移率表明,提出的迁移率计算模型可以比较精确地得到在强场下较大温度范围内的载流子迁移率。该方法为空间介质电荷输运规律和机理的研究提供了基础。

CALCULATION OF CARRIER MOBILITY IN SPACE INSULATER BY THE THERMALLY STIMULATED CURRENT

The charge transport properties of dielectrics determine spacecraft charging level and electrostatic discharging(ESD) probability,affecting the reliability and lifetime of spacecrafts.To investigate the charge carrier mobility of space grade polyimide at various temperatures,a novel method based on Thermally Stimulated Current(TSC) is proposed in present paper.Charges will inject from the electrodes into the material after a high voltage is applied for a while,and been maintained in the traps when the material is frozen with liquid Nitrogen.The trapped charges in the insulator are assumed to satisfy Boltzmann distribution.When the temperature of the sample is increased slowly,the trapped charges will gradually detrap to the conduction band and transport to the contacted electrode.Based on this physical model,we can derive the charge carrier mobility from TSC.We calculate the temperature dependent charge carrier mobility of polyimide film at the temperature range of 173 K~493 K.These results are compared with that measured by space charge limited current method,and they are in good agreement with each other.It may provide an efficient way to study the charge transport characteristics of insulators and help spacecraft engineers better the design of spacecraft shielding.