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

Abstract Al-MoSe_xO_y (un-doped and Al-doped MoSe_xO_y) 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-MoSe_xO_y 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-MoSe_xO_y 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-MoSe_xO_y film channel. The incorporation of the Al makes the ambipolar FET device based on un-doped MoSe_xO_y channel into p-type FET. P-type conductive FET based on 5.2% Al-MoSe_xO_y channel has the highest field-effect mobility (55.2 cm² V^-1 s^-1) and preferable I_on/I_off ratio (∼10⁴).