Analysis of the Solution-Processed a-SnO_X and HfO₂ Interface for Applications in Thin-Film Transistors

Indium gallium zinc oxide is an amorphous oxide semiconductor (AOS) which has been regarded as a substitute for hydrogenated amorphous silicon. Other AOSs have been investigated but have needed multiple cations to reach high mobilities. Nonetheless, amorphous tin oxide (a-SnOx) has demonstrated thin-film transistors (TFTs) with high mobility. Here, we analyze the impact of the interface between the HfO2 dielectric and the tin oxide active layer on the performances of the TFTs. By analysis of electrical (through TFT devices) and chemical (through X-ray photoelectron spectroscopy measurements) properties and using technology computer-aided design, we can understand the origin of the high field-effect mobility (>90 cm2/V s). From the low contact and channel resistances and the large carrier concentration (∼1019 cm–3) to the large conduction band offset (2.59 eV) and the low exponentially distributed conduction band tail state (NTA) of 2.3 × 1019 cm–3 eV–1, the origin of the high performance has been investigated in depth.