Electrical Properties of La-Doped Al₂O₃ Films on Si (100) Substrates as a High-Dielectric-Constant Gate Material

Amorphous La-doped Al₂O₃ (La: Al₂O₃) thin films are deposited on n-type (100) Si substrates by rf magnetron co-sputtering. The composition of the deposited films is measured by energy dispersive x-ray spectroscopy. Capacitance--voltage measurement shows that the dielectric constant k of La-doped Al₂O₃ films ranges from 8.5 to 11.6 with the increasing La content, and the highest k value of 11.6 is obtained for the 20.14% La content film. In the structure of the Al/La:Al₂O₃/Si metal oxide semiconductor, the dominant conduction stems from the space-charge-limited current at different temperatures. In addition, the wavelength dependence of the transmittance is studied by ultraviolet spectroscopy and the band gap of all the deposited films is above 5.5eV. The results demonstrate that La-doped Al₂O₃ can meet the requirement of next-generation gate materials.