Processing
Strategies for High-Performance Schottky Contacts on n‑Type
Oxide Semiconductors: Insights from In2O3
Posted on 2019-07-22 - 04:13
Preparation
of rectifying Schottky contacts on n-type oxide semiconductors, such
as indium oxide (In2O3), is often challenged
by the presence of a distinct surface electron accumulation layer.
We investigated the material properties and electrical transport characteristics
of platinum contact/indium oxide heterojunctions to define routines
for the preparation of high-performance Schottky diodes on n-type
oxide semiconductors. Combining the evaluation of different Pt deposition
methods, such as electron-beam evaporation and (reactive) sputtering
in an (O and) Ar atmosphere, with oxygen plasma interface treatments,
we identify key parameters to obtain Schottky-type contacts with high
electronic barrier height and high rectification ratio. Different
photoelectron spectroscopy approaches are compared to characterize
the chemical properties of the contact layers and the interface region
toward In2O3, to analyze charge transfer and
plasma oxidation processes as well as to evaluate the precision and
limits of different methodologies to determine heterointerface energy
barriers. An oxygen-plasma-induced passivation of the semiconductor
surface, which induces electron depletion and generates an intrinsic
interface energy barrier, is found to be not sufficient to generate
rectifying platinum contacts. The dissolution of the functional interface
oxide layer within the Pt film results in an energy barrier of ∼0.5
eV, which is too low for an In2O3 electron concentration
of ∼1018 cm–3. A reactive sputter
process in an Ar and O atmosphere is required to fabricate rectifying
contacts that are composed of platinum oxide (PtOx). Combining oxygen plasma interface oxidation of the semiconductor
surface with reactive sputtering of PtOx layers results in the generation of a high Schottky barrier of ∼0.9
eV and a rectification ratio of up to 106. An additional
oxygen plasma treatment after contact deposition further reduced the
reverse leakage current, likely by eliminating a surface conduction
path between the coplanar Ohmic and Schottky contacts. We conclude
that processes that allow us to increase the oxygen content in the
interface and contact region are essential for fabrication of device-quality-rectifying
contacts on various oxide semiconductors.
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Michel, Jonas; Splith, Daniel; Rombach, Julius; Papadogianni, Alexandra; Berthold, Theresa; Krischok, Stefan; et al. (2019). Processing
Strategies for High-Performance Schottky Contacts on n‑Type
Oxide Semiconductors: Insights from In2O3. ACS Publications. Collection. https://doi.org/10.1021/acsami.9b06455
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AUTHORS (10)
JM
Jonas Michel
DS
Daniel Splith
JR
Julius Rombach
AP
Alexandra Papadogianni
TB
Theresa Berthold
SK
Stefan Krischok
MG
Marius Grundmann
OB
Oliver Bierwagen
Hv
Holger von Wenckstern
MH
Marcel Himmerlich
KEYWORDS
heterointerface energy barriersPt film resultsoxygen plasma treatmentDifferent photoelectron spectroscopy approachesplasma oxidation processesHigh-Performance Schottky Contactsoxygen plasma interface treatmentsSchottky contactsinterface energy barrier2 O 3 electron concentrationPt deposition methodssurface conduction pathPtO x layers results2 O 3rectification ratiosemiconductor surfaceoxygen plasma interface oxidation2 O 3 Preparationsurface electron accumulation layern-type oxide semiconductorsinterface oxide layer