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金属与Ge材料接触由于存在强烈的费米钉扎效应,导致金属电极与n型Ge接触引入较大的接触电阻,限制了Si基Ge探测器响应带宽.本文报道了在SOI衬底上外延Ge单晶薄膜并制备了不同台面尺度的Ge PIN光电探测器.对比了电极分别为金属Al和Al/TaN叠层的具有相同器件结构的SOI基Ge PIN光电探测器的暗电流、响应度以及响应带宽等参数.发现在Al与Ge之间增加一薄层TaN可有效减小n型Ge的接触电阻,将台面直径为24μm的探测器在1.55μm的波长和-1 V偏压下的3 dB响应带宽提高了4倍.同时,器件暗电流减小一个数量级,而响应度提高了2倍.结果表明,采用TaN薄层制作金属与Ge接触电极,可有效钝化金属与Ge界面,减轻费米钉扎效应,降低金属与n-Ge接触的势垒高度,因而减小接触电阻和界面复合电流,提高探测器的光电性能.
Metal contact with Ge material Due to the Fermi pinning effect, the contact resistance between the metal electrode and the n-type Ge is large, which limits the response bandwidth of the Si-based Ge detector.In this paper, Single crystal thin films were fabricated and Ge PIN photodetectors with different mesa sizes were prepared.The dark current, responsivity and response of SOI-based Ge PIN photodetectors with the same device structure with metal Al and Al / TaN stacks were compared Bandwidth and other parameters.It is found that adding a thin layer of TaN between Al and Ge effectively reduces the contact resistance of n-type Ge, and the detector with a tabletop diameter of 24μm at a wavelength of 1.55μm and a bias voltage of -1dB The response bandwidth is increased by 4 times, meanwhile, the dark current of the device is reduced by one order of magnitude and the responsivity is increased by two times.The results show that the use of TaN thin film to make metal and Ge contact electrode can effectively passivate the interface between metal and Ge, The pinning effect of rice reduces the barrier height of the metal in contact with n-Ge, thereby reducing the contact resistance and interface recombination current and improving the photoelectric property of the detector.