基于周期反转模式的表面暗电流抑制

为了抑制电子倍增CCD的表面暗电流,运用Shockley-Read-Hall理论解释了表面暗电流的产生过程,通过曲线拟合建立了表面暗电流的理论模型,定量分析了电子倍增CCD从反转模式切换到非反转模式后表面暗电流的恢复特征时间.根据这一时间特性提出了周期反转模式的概念,在信号积分期里对成像区时钟进行调制,加入周期反转脉冲,使器件以小于表面暗电流恢复特征时间的周期在反转与非反转模式之间切换.仿真结果表明,随着周期反转频率的提高.表面暗电流明显减小.当时钟周期为0.2 ms时,平均表面暗电流降低到0.051 nA/cm2,接近反转模式的水平,与理论分析完全一致,验证了周期反转模式的可行性.

Suppression of Surface Dark Current Based on Periodic Inverted Mode

In order to suppress surface dark current of electron multiplying CCDs, Shockley-Read-Hall theory is applied to describe the generation progress of surface dark current. The theoretical model of surface dark current is established by curve fitting. Recovery characteristic time of surface dark current is obtained through a quantitative analysis when the device is switched from inverted mode to non-inverted mode. Periodic inverted mode is proposed based on the timing character. Imaging clocks are modulated by periodic inverted pulses during signal integration. The device is switched from inverted mode to non-inverted mode at a period less than surface dark current recovery time. Simulation results show that surface dark current dramatically decreases as periodic inverted frequency increases. When the period equals 0.2 ms, average surface dark current is 0.051 nA/cm2, approaching inverted mode level. The results are in good agreement with theoretical analysis and the feasibility of periodic inverted mode is proved.