Analysis of variation in leakage currents of Lanthana thin films

Lanthana (La2O3) films were deposited by E-beam evaporation on n-Si(1 0 0). Conduction mechanisms for the as-deposited film have been investigated. In order to study the annealing effect of the as-deposited films on the conduction mechanisms, some films were annealed in an ex situ way at different temperatures with nitrogen or oxygen gas flow for 5 min. From current-voltage measurement of the as-deposited films, extremely low gate oxide leakage currents were observed while some films showed variation in the scale of the currents. It is shown that all the currents of as-deposited films obey the same conduction mechanisms irrelevant of the magnitude of the leakage currents. From the electric field and temperature dependences of the currents of the gate oxide, it is shown that the main conduction mechanisms are the space-charge limited current (SCLC) at low oxide field region and Fowler-Nordheim (F-N) conduction at high oxide field region. It is also shown that conduction mechanisms of the nitrogen annealed films were basically the same as those of the as-deposited films although the magnitude of the conduction current and flat-band voltage (VFB) are different.