n型SiC极性面对欧姆接触性质的影响

Effects of Terminated Faces of n-Type SiC on the Property of Ohmic Contacts

研究了n型碳化硅(SiC)极性表面、载流子浓度和退火温度对欧姆接触的影响,测试了不同样品的电流-电压曲线,并通过传输线方法计算比接触电阻。对于SiC衬底的硅面,GeNiTiAu合金材料的欧姆接触特性最好;而对于碳面,TiAu合金材料的接触电阻最小。衬底载流子浓度由1.5×101 7cm-3逐步提高到2.0×1018cm-3,金属与n型SiC衬底硅面的接触由肖特基接触变为欧姆接触,欧姆接触电阻随着载流子浓度的提高而明显降低。GeTiAu合金与SiC衬底硅面的接触电阻随着退火温度的提高非单调降低,900℃为最优退火温度。原子力显微镜结果显示,退火后样品表面粗糙度明显提高。

The effects of the terminated faces,carrier concentration and annealing tempearture on the n-type silicon carbide（ SiC） ohmic contacts were studied. The specific contact resistivities were calculated by the transfer line method（ TLM） according to the current-voltage data of the different samples.For the SiC substrate,GeNiTiAu alloy shows the best ohmic contact on the silicon terminated face,while TiAu alloy has the lowest contact resistivity on the carbon terminated face. Schottky contact behavior changed to ohmic contact between the metal and the silicon terminated face of the n type SiC substrate as the carrier concentration of the SiC substrate increased to 2. 0 × 10^18cm^- 3from 1. 5 × 10^17cm^- 3. Besides,the contact resistivity decreased dramatically as the increase of the carrier concentration. The contact resistivity of GeTiAu on the silicon terminated face of the SiC substrate reduced non-monotonically with the increase of the annealing temperature. The optimal annealing temperature is 900 ℃. The surface roughness of the samples is obviously increased after the annealing as shown by the atomic force microscope（ AFM） images.