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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。
In order to suppress the dark current of electron multiplying CCD surface, Shockley-Read-Hall theory is used to explain the surface dark current generation. The theoretical model of surface dark current is established by curve fitting. Quantitative analysis of the electron multiplying CCD from reverse mode switching Recovery time of surface dark current after non-inversion mode. Based on this time characteristic, the concept of period inversion mode is proposed. During the signal integration period, the clock in the imaging area is modulated and the period inversion pulse is added to make the device restore the characteristic time less than the surface dark current. Switch between modes. Simulation results show that the surface dark current decreases obviously with the increase of the frequency of periodic inversion. When the clock period is 0.2 ms, the average surface dark current is reduced to 0.051 nA / cm2, which is close to the level of the inversion mode, which is completely consistent with the theoretical analysis. The feasibility of the period inversion mode is verified.