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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24 μ的探测器在1.55 μ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.
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关键词:
- Al/TaN /
- 接触电阻 /
- Ge PIN光电探测器 /
- 高频特性
Large contact resistance due to Fermi level pinning effect at the interface between metal and Ge strongly restricts the 3 dB bandwidth of Ge photodetectors. In this paper, the Ge PIN photodetectors fabricated on silicon-on-insulator substrates, respectively, with Al and Al/TaN electrodes are comparatively studied. It is found that 3 dB bandwidth of photodetector with 24 μm mesa diameter using an Al/TaN stack electrode is improved by four times more than that of the same structure Ge PIN photodetector using an Al electrode under -1 V bias at 1.55 μ. In addition, the dark current is reduced by one order of magnitude, and optical responsivity is enhanced by two times. These results suggest that a thin metallic TaN layer as an electrode can effectively passivate the Ge surface and alleviate the Fermi-level pinning effect, thus reducing the contact resistance and the recombination current at the interface. TaN can be considered as a promising electrode material for Ge device applications.-
Keywords:
- Al/TaN /
- contact resistance /
- Ge PIN photodetector /
- high frequency
[1] Michel J, Liu J F, Kimerling L C 2010 Nature Photonics 4 527
[2] Dimoulas A, Tsipas P, Sotiropoulos A, Evangelou E K 2006 Appl. Phys. Lett. 89 252110
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[6] Nishimura T, Kita K, Toriumi A 2008 Appl. Phys. Express 1 051406
[7] Jason Lin J Y, Roy A M, Nainani A, Sun Y, Saraswat K C 2011 Appl. Phys. Lett. 98 092113
[8] Roy A M, Jason Lin J Y, Saraswat K C 2010 IEEE Electron Device Lett. 31 10
[9] Iyota M, Yamamoto K, Wang D, Yang H G, Nakashima H 2011 Appl. Phys. Lett. 98 192108
[10] Wu Z, Huang W, Li C, Lai H K, Chen S Y 2012 IEEE Trans. Electron. Devices 59 1328
[11] Schroder D K 2008 Semiconductor Material and Device Characterization (1st Ed.) (Dalian: Dalian University of Technology press) p108 (in Chinese) [施罗德 2008 半导体材料与器件表征技术(第一版) (大连: 大连理工大学出版社) 第108页]
[12] Giovane L M, Luan H C, Agarwal A M, Kimerling L C 2001 Appl. Phys. Lett. 78 541
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[1] Michel J, Liu J F, Kimerling L C 2010 Nature Photonics 4 527
[2] Dimoulas A, Tsipas P, Sotiropoulos A, Evangelou E K 2006 Appl. Phys. Lett. 89 252110
[3] Chao Y L, Woo J C S 2010 IEEE Trans. Electron. Devices 57 665
[4] Zhou Y, Ogawa M, Han X H, Wang K L 2008 Appl. Phys. Lett. 93 202105
[5] Kobayashi M, Kinoshita A, Saraswat K, Wong H S P, Nishi Y 2008 Dig. Tech. Pap.-Symp. VLSI. Technol. 54
[6] Nishimura T, Kita K, Toriumi A 2008 Appl. Phys. Express 1 051406
[7] Jason Lin J Y, Roy A M, Nainani A, Sun Y, Saraswat K C 2011 Appl. Phys. Lett. 98 092113
[8] Roy A M, Jason Lin J Y, Saraswat K C 2010 IEEE Electron Device Lett. 31 10
[9] Iyota M, Yamamoto K, Wang D, Yang H G, Nakashima H 2011 Appl. Phys. Lett. 98 192108
[10] Wu Z, Huang W, Li C, Lai H K, Chen S Y 2012 IEEE Trans. Electron. Devices 59 1328
[11] Schroder D K 2008 Semiconductor Material and Device Characterization (1st Ed.) (Dalian: Dalian University of Technology press) p108 (in Chinese) [施罗德 2008 半导体材料与器件表征技术(第一版) (大连: 大连理工大学出版社) 第108页]
[12] Giovane L M, Luan H C, Agarwal A M, Kimerling L C 2001 Appl. Phys. Lett. 78 541
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