The effects of interface and bulk defects on the electrical performance of amorphous carbon/silicon heterojunctions

Amorphous diamond-like carbon (DLC)–silicon heterojunctions developed by rf magnetron sputtering from a carbon target on n-type Si(100) substrates at room temperature (RT) with TiN as a metal contact showed a high rectification ratio and asymmetric p–n junction characteristics. Classical current–voltage (I–V) measurements at various temperatures allowed to derive the conduction mechanisms which are directly related to the number of defects in the bulk of the material or at the interface between the Si and the amorphous carbon. Low frequency noise measurements at RT provided the concentration of states or traps that create the fluctuation of the current through the device and was used to clarify their role as far as the electrical properties of the material are concerned. Low temperature admittance spectroscopy was also used to measure the density of interface traps and the results were found to agree with those of the noise measurements. In particular, the density of states was found to be of the order of 1012 eV−1 cm−2 and their time constant of the order of 10−4 s. All of the above were suitably used and used in order to explain the defects contribution on the conduction mechanisms and the device behaviour.