Oxides are among the materials with the widest tunability of physical properties. Spanning insulators, semiconductors, metallic conductors and superconductors, magnetic materials, ferro-/antiferro- and other dielectrics, oxides are a materials class with high potential for a new generation of electronic devices for energy and sensing applications.
Traditionally, oxides have been synthesized by pulsed laser deposition or sputtering, which both have drawbacks in terms of material quality. A higher material quality can be achieved by molecular beam epitaxy (MBE), which is the growth method used by us.
Our research aims at exploring the properties of semiconducting oxides at the materials limit, equally taking into account the understanding of the growth thermodynamics and kinetics as well as the materials application perspective. Providing samples for (international) collaborations is an important part of our scientific culture. To date, our materials portfolio comprises the n-type oxides (Ga,In,Al)2O3, SnO2, the perovskites BaSnO3 and LaInO3, as well as the p-type oxides SnO and (the antiferromagnet) NiO. Out of these SnO2, NiO, and In2O3 are frequently used in conductometric gas sensing—an application whose fundamental investigation together with external collaborators greatly benefits from our well-defined samples. Energy-efficient power electronics as well as solar-blind UV sensing are further important applications, both of which are foreseen to profit tremendously from the ultra-wide bandgap semiconductor Ga2O3 and its solid solutions with In2O3 and Al2O3. For the same purpose, we recently started investigating rutile-GeO2 and its solid solutions with SnO2 and SiO2.
Embedded in the Berlin-based Leibniz ScienceCampus Growth and fundamentals of oxides for electronic applications (GraFOx), led by PDI, our activities are currently divided into the following projects:
- Metastable III2O3 alloys, deep acceptor-doping, and p-type oxides
- MBE of LaInO3/BaSnO3 heterostructures for electronic applications (funding in Leibniz competition “BaSnO3-based heterostructures for electronic applications”)
- Point defects control in Ga2O3 thin films grown via molecular beam epitaxy (funded by DFG)
- (Si,Ge,Sn)O2-based ultra-wide bandgap semiconductors for power electronics (funding in Leibniz competition)
Author: K. Tetzner , K. O. Egbo , M. Klupsch , R.-S. Unger , A. Popp , T.-S. Chou , S. Bin Anooz , Z. Galazka , A. Trampert , O. Bierwagen , J Würfl
Title: SnO/β-Ga2O3 heterojunction field-effect transistors and vertical p-n diodes
Source: Appl. Phys. Lett. , 120 , 112110 ( 2022 )
Author: J. Feldl , M. Feneberg , A. Papadogianni , J. Lähnemann , T. Nagata , O. Bierwagen , R. Goldhahn , M. Ramsteiner
Title: Band gap widening and phonon behavior of cubic single-crystalline (In,Ga)2O3 alloy ﬁlms
Source: Appl. Phys. Lett. , 119 , 042101 ( 2021 )
Author: O. Bierwagen , P. Vogt , P. Mazzolini
Title: Gallium Oxide - Plasma-Assisted Molecular Beam Epitaxy 2—Fundamentals of Suboxide-Related Growth Kinetics, Thermodynamics, Catalysis, Polymorphs, and Faceting
Source: Springer Series in Materials Science , 293 , 95 ( 2020 )
Author: G. Hoffmann , M. Budde , P. Mazzolini , O. Bierwagen
Title: Efficient suboxide sources in oxide molecular beam epitaxy using mixed metal + oxide charges: The examples of SnO and Ga2O
Source: APL Mater. , 8 , 031110 ( 2020 )
Author: J. Rombach , A. Papadogianni , M. Mischo , V. Cimalla , L. Kirste , O. Ambacher , T. Berthold , S. Krischok , M. Himmerlich , Sören Selve , O. Bierwagen
Title: The role of surface electron accumulation and bulk doping for gas-sensing explored with single-crystalline In2O3 thin films
Source: Sens. Actuators B Chem. , 236 , 909 ( 2016 )