Metal-induced n+/n homojunction for ultrahigh electron mobility transistors

Ji-Min Park,Hyun-Suk Kim,Ho-Hyun Nahm,Sanghun Jeon,Yong-Hyun Kim,Kyung Park,Seong Cheol Jang,Hongrae Joh,Hyoung-Do Kim,Yun Chang Park

doi:10.1038/s41427-020-00271-y

Abstract

A self-organized n+/n homojunction is proposed to achieve ultrahigh performance of thin film transistors (TFTs) based on an amorphous (Zn,Ba)SnO3 (ZBTO) semiconductor with sufficiently limited scattering centers. A deposited Al layer can induce a highly O-deficient (n+) interface layer in the back channel of a-ZBTO without damaging the front channel layer via the formation of a metal-oxide interlayer between the metal and back channel. The n+ layer can significantly improve the field-effect mobility by providing a relatively high concentration of free electrons in the front n-channel ZBTO, where the scattering of carriers is already controlled. In comparison with a Ti layer, the Al metal layer is superior, as confirmed by first-principles density functional theory (DFT) calculations, due to the stronger metal-O bonds, which make it easier to form a metal oxide AlOx interlayer through the removal of oxygen from ZBTO. The field-effect mobility of a-ZBTO with an Al capping layer can reach 153.4 cm2/Vs, which is higher than that of the pristine device, i.e., 20.8 cm2/Vs. This result paves the way for the realization of a cost-effective method for implementing indium-free ZBTO devices in various applications, such as flat panel displays and large-area electronic circuits.

Highlights

1234567890():,; 1234567890():,; 1234567890():,; 1234567890():,; Introduction Thin-film transistors (TFTs) with amorphous oxide semiconductors (AOSs) have been incorporated into various display applications owing to their many advantages, such as their relatively high mobility (≥10 cm2/Vs), large-area uniformity, and low-temperature process capability[1,2,3]
The second mechanism is the metal-induced crystallization (MIC) of the active channel layer at low temperatures, which improves the transport of carriers by reducing the number of disorder defects in the channel material[19,22]
We propose ultrahigh-mobility a-ZBTObased TFTs achieved via the formation of an n+/n homojunction induced by a metal-capping layer considering the collaborative outcomes of experiments and density functional theory (DFT) calculations

Summary

Introduction

Thin-film transistors (TFTs) with amorphous oxide semiconductors (AOSs) have been incorporated into various display applications owing to their many advantages, such as their relatively high mobility (≥10 cm2/Vs), large-area uniformity, and low-temperature process capability[1,2,3]. The first is the scavenging effect of the scattering/trapping centers due to the metal layer, implying that the field-effect mobility of the AOSs should be improved due to the reduced scattering[18,19,21]. This can be understood because oxygen-related defects, such as weakly bonded or interstitial oxygen in the active channel layer, are preferentially removed during the formation of a metal-oxide layer[19,21].

Methods

Results

Conclusion