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金属与半导体Ge欧姆接触制备、性质及其机理分析*
Properties and mechanism analysis of metal/Ge ohmic contact*
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摘要: 金属与Ge材料接触时界面处存在着强烈的费米钉扎效应，尤其与n型Ge形成的欧姆接触的比接触电阻率高，是制约Si基Ge器件性能的关键因素之一.本文对比了分别采用金属Al和Ni与Si衬底上外延生长的p型Ge和n型Ge材料的接触特性.发现在相同的较高掺杂条件下， NiGe与n型Ge可形成良好的欧姆接触，其比接触电阻率较Al接触降低了一个数量级，掺P浓度为2×1019 cm?3时达到1.43×10?5?·cm2. NiGe与p型Ge接触和Al接触的比接触电阻率相当，掺B浓度为4.2×1018 cm?3时达到1.68×10?5?·cm2. NiGe与n型Ge接触和Al电极相比较，在形成NiGe过程中， P杂质在界面处的偏析是其接触电阻率降低的主要原因.采用NiGe作为Ge的接触电极在目前是合适的选择.Abstract: Large contact resistance due to Fermi level pinning effect at the interface between metal and n-type Ge strongly restricts the performance of Ge device on Si substrate. In this paper, the contacts of metal Al and Ni with n-type Ge and p-type Ge epitaxial layers grown by UHV/CVD are comparatively studied. It is found that the contact of NiGe/n-Ge is better than that of Al/n-Ge at the same dopant concentration. When the concentration of P is 2 × 1019 cm?3 , the ohmic contact of NiGe/n-Ge withρc down to 1.43× 10?5?·cm2 is demomstrated, which is about one order of magnitude lower than that of Al/n-Ge contact. The specific contact resistance of NiGe/p-Ge is 1.68 × 10?5?·cm2 when the B concentration is 4.2 × 1018 cm?3, corresponding to that of Al/p-Ge. Compared with Al/n-Ge contact, P segregation at the interface between NiGe and Ge, rather than lowering Schottky barrier height, is the main reseaon for achieving the low specific contact resistance. NiGe/Ge contact should be a good choice for contact electrode for Ge devices at present.
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