不同介质层钝化的碲镉汞光导型探测器的氢化研究

利用氢等离子体对阳极氧化层和ZnS钝化的碲镉汞光导型探测器进行了氢化处理,发现对于阳极氧化层钝化的器件,氢化处理后性能衰退,表现在信号的降低和噪声的增加,从表面形貌的观察,发现原来呈蓝色的阳极氧化层在氢化处理后几乎完全消失,从光谱响应上表现为短波方向的响应下降,认为由于氢化过程中介质层的消失使得氢离子直接轰击碲镉汞表面,造成少子表面复合速度增加.对ZnS钝化的器件氢化处理后性能改善,表现为信号的提高和噪声的下降,从光谱响应上表现为短波方向的响应抬高,从表面形貌观察发现ZnS的颜色略有变化,台阶仪测试表明氢化后ZnS的厚度减薄了约70nm,通过SIMS测试分析发现氢化过程中H离子可以穿过ZnS层到达ZnS与碲镉汞的界面处,认为氢离子对界面态起到了钝化作用,降低了界面态密度从而提高了器件的性能.

Study of Hydrogenation on HgCdTe Photoconductive Detectors Passivated with Different Dielectrics

The hydrogenation of HgCdTe photoconductive(PC) detectors passivated with anodic oxide(AO) and ZnS by H-plasma has been investigated.After hydrogenation the detectors passivated with AO showed a degradation of performance with lower signal and higher noise.From the surface topography of the sample,the original blue anodic oxide almost disappeard,and from rcsponsivity spectrum,the responsivity in the shorter wavelength direction was depressed. It was considered that H ions directly bombarded the HgCdTe surface after the AO was consumed,which induced an increase in surface recombination velocity of the minority carriers.However,for detectors passivated with ZnS,the performance was improved after hydrogenation,showing higher signal and lower noise,and from the FTIR spectrum the responsivity in the shorter wavelength direction was lifted up.From surface topography a slight change was found for the color of ZnS, and a step of about 70nm appeared by XP-2 step profiling.With SIMS analysis H was found to penetrate through ZnS and reach the interface between ZnS and HgCdTe,and the improvement of performance after hydrogenation was thought due to the passivation of interface states by H ions.