Conduction mechanism of hydrogenated nanocrystalline silicon films

Abstract

A heteroquantum dot (HQD) tunneling model for the conduction mechanism of hydrogenated nanocrystalline silicon films is proposed. The main features of the HQD model follow. (i) The micrograins and their amorphous counterparts have very different band gaps and band structures; as a result, they form a heterojunctionlike structure in interface regions where the band offset dramatically reduces the activation energy of electrons and the micrograins act as a quantum dot (QD). (ii) In the presence of an external field, activated electrons have ballistic properties in the QD's and quantum tunneling processes through the interface barriers. Based on this model, an equation for the conductivity of nc-Si:H films is deduced, and the calculated results are in good agreement with the experimental results. Using nc-Si:H thin layers a resonant tunneling diode with quantum characteristics was fabricated.