2 research outputs found
<i>In Situ</i> Chemical Modification of Schottky Barrier in Solution-Processed Zinc Tin Oxide Diode
Here
we present a novel <i>in situ</i> chemical modification
process to form vertical Schottky diodes using palladium (Pd) rectifying
bottom contacts, amorphous zinc tin oxide (Zn–Sn–O)
semiconductor made via acetate-based solution process, and molybdenum
top ohmic contacts. Using X-ray photoelectron spectroscopy depth profiling,
we show that oxygen plasma treatment of Pd creates a PdO<sub><i>x</i></sub> interface layer, which is then reduced back to metallic
Pd by <i>in situ</i> reactions during Zn–Sn–O
film annealing. The plasma treatment ensures an oxygen-rich environment
in the semiconductor near the Schottky barrier, reducing the level
of oxygen-deficiency-related defects and improving the rectifying
contact. Using this process, we achieve diodes with high forward current
density exceeding 10<sup>3</sup>A cm<sup>–2</sup> at 1 V, rectification
ratios of >10<sup>2</sup>, and ideality factors of around 1.9.
The measured diode current–voltage characteristics are compared
to numerical simulations of thermionic field emission with sub-bandgap
states in the semiconductor, which we attribute to spatial variations
in metal stoichiometry of amorphous Zn–Sn–O. To the
best of our knowledge, this is the first demonstration of vertical
Schottky diodes using solution-processed amorphous metal oxide semiconductor.
Furthermore, the <i>in situ</i> chemical modification method
developed here can be adapted to tune interface properties in many
other oxide devices
High Performance, Low Temperature Solution-Processed Barium and Strontium Doped Oxide Thin Film Transistors
Amorphous mixed metal oxides are
emerging as high performance semiconductors
for thin film transistor (TFT) applications, with indium gallium zinc
oxide, InGaZnO (IGZO), being one of the most widely studied and best
performing systems. Here, we investigate alkaline earth (barium or
strontium) doped InBaÂ(Sr)ÂZnO as alternative, semiconducting channel
layers and compare their performance of the electrical stress stability
with IGZO. In films fabricated by solution-processing from metal alkoxide
precursors and annealed to 450 °C we achieve high field-effect
electron mobility up to 26 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>. We show that it is possible to solution-process
these materials at low process temperature (225–200 °C
yielding mobilities up to 4.4 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>) and demonstrate a facile “ink-on-demand”
process for these materials which utilizes the alcoholysis reaction
of alkyl metal precursors to negate the need for complex synthesis
and purification protocols. Electrical bias stress measurements which
can serve as a figure of merit for performance stability for a TFT
device reveal Sr- and Ba-doped semiconductors to exhibit enhanced
electrical stability and reduced threshold voltage shift compared
to IGZO irrespective of the process temperature and preparation method.
This enhancement in stability can be attributed to the higher Gibbs
energy of oxidation of barium and strontium compared to gallium