HgCdTe长波光伏探测器的表面漏电流及1/f噪声研究

在同一Hg_1-xCd_xTe晶片上(x=0217)制备了单层ZnS钝化和双层 （CdTe+ZnS）钝化的两种器件，对器件烘烤前后的暗电流和1/f噪声进行了测试，烘烤 前发现，ZnS钝化的器件在反偏较大时具有较大的表面隧道电流，而这种表面漏电流是ZnS钝 化器件具有较大1/f噪声电流的原因，通过高分辨x射线衍射中的倒易点阵技术（recipr ocal space mapping,RSM）研究了单双层钝化对HgCdTe外延层晶格完整性的影响，发现单层 ZnS钝化的HgCdTe外延层产生了大量缺陷，而这些缺陷正是ZnS钝化器件具有较大表面漏电流 和1/f噪声的原因. 经过高温烘烤后，ZnS钝化的器件暗电流和1/f噪声增加，而双 层钝化器件经过高温烘烤后性能提高. RSM的研究表明，高温烘烤后ZnS钝化的HgCdTe外延层 产生大量缺陷，这些缺陷正是单层钝化器件表面漏电流和1/f噪声电流增加的原因. 关键词： HgCdTe 光伏探测器 钝化 表面漏电流 1/f噪声 倒易点

Analysis of surface leakage and 1/f noise on long-wavelength infrared HgCdTe photodiodes

The long-wavelength infrared Hg_1-xCd_xTe photovoltaic dete ctors with x=0217 passivated by single ZnS layer and dual (CdTe+ZnS) layers were fabricated in the same wafer. The fabricated devices were characterized by meas urements of dark currents and 1/f noise. The diode passivated by dual (CdTe+ ZnS) layers showed a higher performance compared to the diode passivated by the single ZnS layer at high reverse bias, and modeling of diode dark current mechan isms indicated that the performance of the diode passivated by single ZnS was st rongly affected by tunneling current related to the surface defects, which was r esponsible for the dark currents and 1/f noise characteristics. By the analy sis of x-ray reciprocal space map (RSM), it was found that the Q_y dir e ction broadening of HgCdTe epitaxial layer passivated by ZnS was wider after pas sivation, which confirmed the existence of defects in the surface of HgCdTe epit axial layer passivated by ZnS. In order to investigate the effect of surface pas sivation on the stability of two kinds of diodes, dark currents and 1/f nois e of the diodes were measured after vacuum baking for 10 h at 80℃. The dark cur rent mechanisms indicated that the performance of the diode passivated by single ZnS was strongly affected by the surface defects. By the analysis of RSM, It wa s found that the Q_y direction broadening of HgCdTe epitaxial layer pa s sivated by ZnS was wider after high-temperature baking, which also confirmed the existence of defects in the surface of HgCdTe epitaxial layer passivated by ZnS after baking.