Solution-processed Ga-Cd-O thin-films with tunable bandgaps and their transistors

Ga-Cd-O (GCO) thin films with different Ga contents were fabricated based on a solution-processed method. The direct optical bandgap of GCO films is changed from 2.89 to 4.53 eV with the Ga-content from 30% to 100% and their relationship agrees well with a second-order equation. The Raman spectra of GCO are dominated by three main features: a relatively sharp peak at similar to 260 cm(-1) and two broad features at similar to 405 and 949 cm(-1), and their variations with the Ga-content are analyzed associated with their phonon mode assignment. Moreover, thin-film transistors using the GCO channels all exhibit n-type transistor characteristics and the evolution of their key electrical parameters with the Ga-content is well elucidated by the structural and morphological properties. A saturation field-effect mobility of 5.1 cm(2) V-1 s(-1), on/off current ratio of 2.1 x 10(7), subthreshold slop of 0.83 V/dec, and threshold voltage of -6.8 V were achieved by the 50% Ga-content device.