An Empirical Modeling of Gate Voltage-Dependent Behaviors of Amorphous Oxide Semiconductor Thin-Film Transistors including Consideration of Contact Resistance and Disorder Effects at Room Temperature.

Sungsik Lee

doi:10.3390/membranes11120954

Abstract

In this paper, we present an empirical modeling procedure to capture gate bias dependency of amorphous oxide semiconductor (AOS) thin-film transistors (TFTs) while considering contact resistance and disorder effects at room temperature. From the measured transfer characteristics of a pair of TFTs where the channel layer is an amorphous In-Ga-Zn-O (IGZO) AOS, the gate voltage-dependent contact resistance is retrieved with a respective expression derived from the current–voltage relation, which follows a power law as a function of a gate voltage. This additionally allows the accurate extraction of intrinsic channel conductance, in which a disorder effect in the IGZO channel layer is embedded. From the intrinsic channel conductance, the characteristic energy of the band tail states, which represents the degree of channel disorder, can be deduced using the proposed modeling. Finally, the obtained results are also useful for development of an accurate compact TFT model, for which a gate bias-dependent contact resistance and disorder effects are essential.

Highlights

Amorphous semiconducting materials such as amorphous Silicon and amorphous oxide semiconductors (AOSs) have been widely used as the channel layer for thin-film transistors (TFTs) [1,2,3]
It is known that these non-ideal properties have a significant influence on the electrical performances of the AOS TFTs [2,3,8]; for example, the field-effect mobility of AOS TFTs is inversely proportional to the density of the localized tail states, while poor contact can lead to a higher contact resistance, and a lower mobility [9]
To capture gate bias-dependent contact resistance (RC) and Intrinsic channel conductance (Gint) in the AOS TFT, an empirical method is proposed based on transfer characteristics measured for the two different AOS TFTs, as the parasitic effects are reflected in the current-voltage characteristics of the transistors

Summary

Introduction

Amorphous semiconducting materials such as amorphous Silicon and amorphous oxide semiconductors (AOSs) have been widely used as the channel layer for thin-film transistors (TFTs) [1,2,3]. With a low temperature process, the AOS film is more likely to be in amorphous phase; the inevitable presence of localized traps (e.g., deep and tail states) is associated with structural disorder in the amorphous phase [2,6] This alludes to a poor quality of metal contacts at the source and drain [1,2,7]. To capture gate bias-dependent contact resistance (RC) and Intrinsic channel conductance (Gint) in the AOS TFT, an empirical method is proposed based on transfer characteristics measured for the two different AOS TFTs, as the parasitic effects are reflected in the current-voltage characteristics of the transistors. TamFTisn(eid.e.T, FthTrse)e, ipsauirsseadretoavreatirlaiebvle aths ethgraeteecvoomltbaignea-tdioenpsemndaednet fRroCmantdhrGeeintexwahmilieneadppTlFyTins)g, iasnuasneadlytoticraeltreixepvreetshsieognadteervivoeltdagfreo-dmeptheencduernrtenRtC–vaonldtaGgeintrewlahtiloenaspopf lTyFinTgs.aBnasaendaloynticthael erxetprriesvseidontrdeenrdivoefdtfhreomRCthves.cVuGrSr,ewnth–ivcohltiasgme oredlaetliloednswoifthTFaTps.oBwaesredlaown, the rGetinrticeavnedaltsroenbde oafcctuhreaRteClyvesx. trVaGcSte, dwahnidchmisodmeolldedel,lyedielwdinthg athpeocwhaerralcatwer,istthiec eGninetrgcyanofablsaondbetaaiclcsutartaetselays eaxmtraecatseudreanodf dmiosodredlleerds,(yaisesludminigngthtehcehdaroamctienraisntcice eonfetrhgeytoraf pb-alnimdittaeidl sctoatnedsuacstiaomn)e. aFsruorme othf edsiesorredseurlsts(,aistsiusmfoinugndthtehdaot mthienagnactee-obfiatshedetrpaepn-dlimenicteiedscoofnbdoutchtiRonC )a. nFdroGmintthaeresewreeslluletxs-, iptliasinfoedunwditthhaatptohwe egra-tlea-wbifausndcetipoenn.dFeinnaclileys, oitfibsobtehliRevCeadntdhaGt itnht earperewseenllteedxprleasiunletsdcwouitlhd abepouwseefru-llafworfaunncatciocunr. aFtienacollmy, pitaicstbTeFliTevmedodthela,twthheepreretsheentgeadter-ebsiuasltsdceopuelnddbenecuiesesfoufl ftohre acnonatcaccutrraetseisctoamncpeacatnTdFdTismoorddeerl,ewffheecrtes athree gcrautec-ibaila. s dependencies of the contact resistance and disorder effects are crucial

Materials and Methods

Mathematical Formulations for AOS TFTss

Contact Resistance and Transfer Characteristics of two TFTs

Conclusions