Effect of semiconductor surface homogeneity and interface quality on electrical performance of inkjet-printed oxide...

In semiconductor technology, the crystallite size of semiconductors is often directly correlated with their superior intrinsic and device mobility. However, when solution-processed, large crystals may bring in higher surface roughness and layer inhomogeneity, which can deteriorate the interface quality and device performance. Along this line, a thorough study on printed oxide field-effect transistors (FETs) has been performed, where the relative significance of crystallite size, surface roughness and spatial homogeneity are evaluated. The comprehensive investigations suggest the spatial homogeneity to be more important than crystallite size in solution processed/printed devices. It is demonstrated that the addition of a small amount of high boiling point polyol in the precursor ink can create large nucleation sites, resulting in reduced average crystallite size, superior inter-particle neck formation, and high spatial homogeneity. Interestingly, carefully estimated device mobility of these polyol-derived In₂O₃ FETs (∼50-55 cm² V^-1 s^-1) is found to be larger than the FETs prepared without polyols, although the crystallite size of the former is an order of magnitude smaller. The high spatial homogeneity and the large mobility values of the polyol-derived In₂O₃ transistors, as compared to the amorphous oxide FETs, lowers the importance of the latter, at least within the solution-processed/printed electronics domain.