Compared with n-GaAs systems, it is hard to find suitable metal
contact for p-Ge substrate to form tunneling effect. Therefore, Pt
metal were chosen as contact metal due to the high work function
of 5.65 eV which can reduce the height of the energy barrier
between the Cu/Pt/Ti metal and the Ge substrate [9]. The results
of the Auger analysis for the Pt/Ti/Pt structure are shown in
Fig. 4. The bottom Pt layer diffused into the Ti and Ge layers, resulting
in a lower contact resistance for the contact. In addition, it is
observed that the Cu atoms did not completely penetrate the top
Pt layer