Composition and optical properties of amorphous Al-MoSexOy thin films and electrical characteristics of Al-MoSexOy field effect transistors

Al-MoSexOy (un-doped and Al-doped MoSexOy) films are prepared by radio frequency (RF) magnetron sputtering, and influence of the Al doping contents on the structure, composition and optical properties of the Al-MoSexOy films has been studied. We find that the amount of the Al can modulate the Mo4+/Mo5+/Mo6+ composition ratios and tune the optical band gap of the Al-MoSexOy film. The concentrations of the higher molybdenum oxidation states (Mo5+, Mo6+) increase, and the value of the band gap increase from 1.86 to 2.90 eV with the increment of the Al doping contents. Back-gated field effect transistors (FETs) have been fabricated and investigated by utilizing the sputtered Al-MoSexOy film channel. The incorporation of the Al makes the ambipolar FET device based on un-doped MoSexOy channel into p-type FET. P-type conductive FET based on 5.2% Al-MoSexOy channel has the highest field-effect mobility (55.2 cm2 V−1 s−1) and preferable Ion/Ioff ratio (∼104).