Barrier height and interface characteristics of Au/Mn5Ge3/Ge(111) Schottky contacts for spin injection

The interface states in Au/Mn5Ge3/Ge Schottky barrier diodes prepared for spintronic applications are investigated using dc I-V-T as well as ac admittance measurements. The latter were performed under forward and reverse biases over a wide range of frequencies ( 1 kHz-3 MHz) while varying the temperature from 50 to 300 K. Variations of the ideality factor with temperature are related to the density of interface states, the presence of which is also evidenced as an excess capacitance in the capacitance-frequency characteristics as well as a peak in the conductance versus frequency. The temperature dependence of these interface state densities, determined to be of the range 10(13)-10(14) eV(-1) cm(-2), and their energy distribution with respect to the bottom of the conduction band are examined.