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

MnGeC compound is of great interest for spintronics applications. The various parameters of Au/MnGeC/Ge(1 1 1) and Au/MnGeC/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 MnGeC/Ge contact is described with a single Gaussian distribution and a conduction mechanism mainly based on the thermoionic emission. On the other hand the MnGeC/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.