High-Mobility Field-Effect Transistors Based on Single-Crystalline ZnO Channels

Abstract

We have fabricated field-effect transistors with single-crystalline ZnO channels consisting of high-quality epitaxial films grown on lattice-matched (0001) ScAlMgO4 substrates by laser molecular-beam epitaxy. Amorphous alumina gate insulators are deposited on the top of the ZnO films using either RF magnetron sputtering or electron-beam evaporation. The field-effect mobility (µFE) of the device prepared by the latter method is as high as 40 cm2·V-1·s-1, one order of magnitude higher than those typically observed for polycrystalline channel devices. However, hysteresis appears in transfer characteristics. This unfavorable effect is found to be eliminated by the thermal annealing of the entire devices in air. The much larger hysteresis and lower µFE are observed for the device with sputtered gate insulators. This is presumably due to dense surface states created by ion or electron bombardment during the sputtering.

Combustion synthesis, characterization and Raman studies of ZnO nanopowders

“…This large exciton binding energy provides excitonic emission more efficiently even at higher temperature. Due to its wide bandgap, ZnO is transparent in the visible part of the electromagnetic spectrum and can therefore be used as a transparent conducting oxide [4], UV-sensitive and solar-blind photodetector [5], shield against high-energy radiation [6], organic light-emitting diodes (O-LED) [7] and transparent thin-film transistors (TTFT) [8]. Some of the field-effect transistors even use ZnO nanorods as conducting channels [9,10].…”

Dielectric Passivation of ZnO-Based Schottky Diodes

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] The focus was mostly on optimization of the rectifying properties by pretreatment of the ZnO surface using wet chemical methods 4,8,9,10,14 or remote plasma treatment 3,4,6,7 or the usage of Schottky diodes for material characterization, 2,5,15 as photodetectors 1,16 or as gates in field-effect transistors. 11,17 Recently, a major breakthrough presenting a simple and reproducible route for the fabrication of high-quality Schottky barriers on ZnO by reactive direct-current (DC) sputtering of the Schottky contact metal was published. 13 Using such diodes it was possible for the first time to determine an experimental value for ZnO's Richardson constant similar to the value expected theoretically.…”

Reinforced Self‐Assembled Nanodielectrics for High‐Performance Transparent Thin Film Transistors

“…Further increasing the positive V G sweep range results in a slight backward scanning current increase with no obvious effect on the forward scan characteristics ( Figure S2, Supporting Information), suggesting that this slight hysteresis may arise from known polarization and/or mobile ion effects. [36][37][38] The μ FE and V T values extracted from the forward I DS 1/2 vs. V G plots are ∼ 180 cm 2 /V · s and ∼ 0.20 V, respectively. The origin of the high μ FE likely refl ects: 1) a conformal, contiguous, chlorine-free (evidenced by a negligible Cl 1s signal and a single symmetric O 1s signal in the XPS spectrum; Figure S3, Supporting Information) v-SiO x layer having properties similar to those of the thinner SAND capping layer, known to dramatically reduce interface trap state densities, as established by low frequency noise and I -V measurements, and to enhance mobility for diverse oxide fi lms and nanowires.…”