Remarkably High-Performance Nanosheet GeSn Thin-Film Transistor.

Te Jui Yen,Albert Chin,Weng Kent Chan,Vladimir Gritsenko,Hsin-Yi Tiffany Chen

doi:10.3390/nano12020261

Abstract

High-performance p-type thin-film transistors (pTFTs) are crucial for realizing low-power display-on-panel and monolithic three-dimensional integrated circuits. Unfortunately, it is difficult to achieve a high hole mobility of greater than 10 cm2/V·s, even for SnO TFTs with a unique single-hole band and a small hole effective mass. In this paper, we demonstrate a high-performance GeSn pTFT with a high field-effect hole mobility (μFE), of 41.8 cm2/V·s; a sharp turn-on subthreshold slope (SS), of 311 mV/dec, for low-voltage operation; and a large on-current/off-current (ION/IOFF) value, of 8.9 × 106. This remarkably high ION/IOFF is achieved using an ultra-thin nanosheet GeSn, with a thickness of only 7 nm. Although an even higher hole mobility (103.8 cm2/V·s) was obtained with a thicker GeSn channel, the IOFF increased rapidly and the poor ION/IOFF (75) was unsuitable for transistor applications. The high mobility is due to the small hole effective mass of GeSn, which is supported by first-principles electronic structure calculations.

Highlights

Single-hole energy bands and small hole effective masses have been reported in metal-oxide SnO materials, the hole mobility of p-type thin-film transistors (pTFTs) is restrained by the requisite low-temperature process [22]
We report poly-GeSn pTFT with a high μFE (41.8 cm2 /V·s), a sharp subthreshold swing (SS) (311 mV/dec), and a large ION /IOFF value (8.9 × 106 )
The hole mobility values increase with the GeSn layer thickness, which is consistent with the increasing trend of ION

Summary

Introduction

Thin-film transistors (TFTs) [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29] have been investigated intensively in the past few decades [1,2,3] because of their ultra-low-energy-using process, usage of a small amount of material, and light transparency [4,5,6,7]. For oxide nTFTs, excellent device performance with a high field-effect mobility (μFE ), of ~100 cm2 /V·s; a sharp turn-on subthreshold swing (SS), of ~100 mV/dec; and a large on-current/off-current (ION /IOFF ) ratio, of >106 , has been achieved using a SnO2 channel material [16,17,18,19,20]. 10 cm2 /V·s [22,23,24,25], which remains a basic challenge for CTFTs. single-hole energy bands and small hole effective masses have been reported in metal-oxide SnO materials, the hole mobility of pTFTs is restrained by the requisite low-temperature process [22]. We report poly-GeSn pTFT with a high μFE (41.8 cm2 /V·s), a sharp SS (311 mV/dec), and a large ION /IOFF value (8.9 × 106 ).

Methods

Results

Conclusion