Heterojunction — A comprative study

To investigate the transport properties of the heterojunction formed by carbon nano tubes, and Silicon carbide nanotubes, the structures are designed using virtual nano lab. The heterojunction were first obtained through a geometry optimization processes. Based on the results of optimization, two-probe systems of the heterojunction were designed and its transport properties were calculated with a method resulting due to modification of non-equilibrium Green's function (NEGF) with density functional theory (DFT). We found that, if we plot a transmission coefficient T(E) as a function of energy, we got a transmission gap of about 1.225 ev, which means that in this energy range the possibility of an electron to transfer from one electrode to another is nearly zero. We further found that the highest occupied molecular orbital (HOMO) has a higher electron density on the CNT section and the lowest unoccupied molecular orbital (LUMO) mainly concentrates on the interface and the Silicon carbide nanotubes section. If we plot I-V curve of the heterojunction the curve can be divided into three regions i.e. if the bias voltage is less than -2.275V the current decreases with decrease in voltage, if it is in between -2.225 to 1.775 V, the current is nearly zero, and if bias is greater than 1.775 V, the current increases with an increase in voltage.