Charge transport properties of high-mobility indium–gallium–zinc oxide thin-film transistors fabricated through atomic-layer deposition

Abstract

Atomic-layer deposition (ALD) is considered a promising method for the fabrication of high-quality indium–gallium–zinc oxide (IGZO) films because of its excellent film conformity and ability to suppress impurities. However, the charge transport properties of thin-film transistors (TFTs) with ALD-based IGZO active channels do not align with existing multiple-trapping- and-release models. In this study, high-mobility TFTs, designed for low-voltage (5 V) operation, are developed with ALD-based IGZO channels, which exhibit a high field-effect mobility of 14 cm² V⁻¹ s⁻¹, on/off ratio of 3.8 × 10⁸, threshold voltage of −0.5 V, and low subthreshold swing of 86 mV dec⁻¹. The charge transport properties of IGZO TFTs fabricated through ALD are investigated by temperature-dependent mobility and time-domain transient analyses and compared with those of IGZO TFTs fabricated through sol–gel coating and sputtering using the same device configuration for the first time. The ALD-based IGZO TFT exhibits a signficantly lower activation energy and higher carrier velocity (3 meV and 9000 cm s⁻¹, respectively) compared with those of the sol–gel-based IGZO TFT (65 meV and 2000 cm s⁻¹) and sputter-based IGZO TFT (37 meV and 4000 cm s⁻¹), which is ascribed to the enhanced metal-oxygen bonding states of the high-quality IGZO film and interfaces between the channel and dielectric layers.