碲镉汞APD平面型PIN结构仿真设计

Device design of planner PIN HgCdTe avalanche photodiode

碲镉汞(HgCdTe)线性雪崩焦平面因其相对低的过剩噪声、较小的工作电压、线性可调等优点,得到了广泛关注。基于电子雪崩中波HgCdTe PIN二极管结构,开展暗电流模型和Okuto-Crowell增益模型仿真。通过改变器件材料结构参数模拟不同电压下的暗电流和增益特性。计算讨论了不同I区(本征区)厚度和载流子浓度对器件暗电流和增益的影响。结果表明结区峰值场强的变化会导致直接隧穿(BBT)电流产生率数量级上的剧烈变化;增加I区厚度和降低I区掺杂浓度可有效抑制BBT电流;增益随场强的变化趋势与BBT电流随场强的变化趋势一致;因此抑制BBT电流的措施会造成增益性能的下降,需要优化参数以获得最佳性能。综合考虑暗电流和增益性能,I区的厚度应不小于3μm,I区浓度需控制在5×10^(14)cm^(-3)以下。单元中波APD的增益实验结果与仿真数据较好地吻合,表明了理论模型的正确性。

HgCdTe avalanche photodiodes(APDs)of linear mode have attracted much attention for their prospective applications,due to the lowest excess noise close to zero,operating bias in the range of-12~0V,and linear gain tunable as well.In this paper,we investigated the dark current mechanism and Okuto-Crowell model based on the PIN structure of mid-wave infrared HgCdTe e-APD.The characteristics of dark current and the gain were simulated.The thickness and carriers concentration of intrinsic region were discussed,which would impact on the dark current and the gain.The results indicated that the peak intensity of electric field would significantly increase the band to band generation,even up to several orders of magnitude.BBT current could be suppressed by increasing the thickness of the intrinsic region,as well as reducing the carrier concentration.Unfortunately,the gain and BBT current would both increase with electric field.The gain normalized dark current(GNDC)is prospective by means of tradeoff between the dark current and the gain.In our studies,intrinsic region with 3μm and the concentration less than 5×1014cm-3 are optimal.The APD I-V results demonstrated that the theoretical model was identical with the experimental data.