Determination of gap states density in PECVD a-Si:H from amorphous-crystalline heterojunctions

The existence of space charge limited currents in n-type amorphous silicon on p-type crystalline silicon heterojunctions has been used to determine the density of states in the gap of the n type a-Si:H. In such a way an indicative measurement of the density of states can be routinely carried out when investigating the use of these heterojunctions in electronic devices. The results show that the localised states distribution can be approximated by an exponential distribution in the range of the scanned energies.