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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2×1019cm-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4.2×1018cm-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.
Ferromagnetic pinning effect exists at the interface of metal and Ge material, especially the ohmic contact with n-type Ge is higher than that of ohmic contact, which is one of the key factors to control the performance of Si-based Ge device.In this paper, The contact characteristics of Al and Ni doped with p-type Ge and n-type Ge epitaxially grown on Si substrate were respectively investigated. It was found that NiGe and n-type Ge formed good ohmic contact under the same higher doping conditions, The contact resistivity is lower by one order of magnitude than Al contact and 1.43 × 10-5 · cm 2 when the P concentration is 2 × 10 19 cm -3. The contact resistivities of NiGe and p-type Ge contacts are comparable to those of Al, Is 1.68 × 10-5 cm 2 for 4.2 × 10 18 cm -3. The segregation of P impurities at the interface during the formation of NiGe is the main reason for the decrease of contact resistivity Contact electrodes using NiGe as Ge are currently the right choice.