Surface analysis and electrical measurement of the ohmic contact on p-CdZnTe (111)B face with Au/Cd composite electrode

摘要

CdZnTe crystal has proved to be an excellent material to detect X-ray and gamma ray. Ohmic electrode on CdZnTe wafer is one of the key factors during the fabrication of CdZnTe detector. In this work, the effect of Au/Cd composite electrode on the (111)B (Te-rich surface) of CdZnTe wafers with p-type conductivity (p-CdZnTe) was investigated. The Au/Cd electrode was deposited on the (111)B of CdZnTe wafers by vacuum evaporation method. For comparison, the Au/Zn and Au electrodes were also deposited on CdZnTe (111)B surfaces. The surface and structural properties of the composite electrodes on the (111)B surface of CdZnTe were characterized by the AFM, XPS and SEM. The electrical properties of the electrodes were evaluated by Current-Voltage (I-V) test. The results show that the surfaces of the Au/Cd and Au/Zn electrodes on (111)B surface were more smooth with less foreign impurities among the interface of the electrode and CdZnTe, as compared to the Au electrode on (111)B surface. The Au/Cd composite electrode can obtain a more ideal ohmic contact than Au/Zn composite electrode on the (111)B surface of CdZnTe wafer. The Au/Cd composite electrode on (111)B surface has the lowest Schottky barrier height, which is attributed to the reduction of the influence of Te enriched surface on the metal-semiconductor contact.