Mn₅Ge₃C_0.6 /Ge(1 1 1) Schottky contacts tuned by an n-type ultra-shallow doping layer

Mn₅Ge₃C_x compound is of great interest for spintronics applications. The various parameters of Au/Mn₅Ge₃C_0.6/Ge(1 1 1) and Au/Mn₅Ge₃C_0.6/ δ -doped Ge(1 1 1) Schottky diodes were measured in the temperature range of 30–300 K by using current–voltage and capacitance–voltage techniques. The Schottky barrier heights and ideality factors were found to be temperature dependent. These anomalous behaviours were explained by Schottky barrier inhomogeneities and interpreted by means of a Gaussian distribution model of the Schottky barrier heights. Following this approach we show that the Mn₅Ge₃C_0.6/Ge contact is described with a single Gaussian distribution and a conduction mechanism mainly based on the thermoionic emission. On the other hand the Mn₅Ge₃C_0.6/ δ -doped Ge contact is depicted with two Gaussian distributions according to the temperature and a thermionic-field emission process. The differences between the two types of contacts are discussed according to the distinctive features of the growth of heavily doped germanium thin films. (paper)