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Terahertz Materials and Advanced Ellipsometry

Graphene and 2D electronic materials

Contemporary CMOS technology is stretched to its scaling limits and new materials with superior transport properties are pursued to fuel the increasing demands of high-speed electronics. To address these issues we explore the potential of epitaxial graphene grown on SiC and 2D electronic systems such 2DEG in AlInN/GaN and AlGaN/GaN. We study the electronic, transport and structural properties of graphene and 2D electronic systems and provide feedback to the growth. We explore different substrate polytypes, surface orientations, surface treatments and modifications to establish the mechanisms that control doping and electronic properties in graphene and AlIn(Ga)N/GaN. The research aims at enabling the desired transport and electronic properties in these materials in order to achieve substantial advance towards high-speed and THz-frequency large scale processor technologies.

Research financed by SSF, VR and VINNOVA

Cooperation with Graphensic AB

InN and related alloys

InN is a narrow band gap (0.6 eV) semiconductor, holding a great potential, when alloyed with GaN (3.4 eV) and AlN (6.0 eV), for highly efficient solar cells, a variety of optoelectronic devices operating from the near-IR to deep UV, THz emitters, high-frequency transistors and sensors. Strong variation of carrier concentration across the thickness of InN layers is observed. The underlying doping mechanisms are highly debated and the mechanisms to control free-charge carrier properties are not yet identified, which precludes the application of InN-based materials. Our major goal is to study and understand the physical mechanisms responsible for the bulk and surface doping and surface charge behavior of InN and related alloys. In particular, we study the effect of surface orientation, crystal modification, defects and doping on the surface charge accumulation and bulk doping in epitaxial InN and InGa(Al)N films. We also study alloying effects on phonons, elastic properties, piezoelectric polarization and strain in InAlN films and nanostructures.

Research financed by VR and FCT, Portugal

Cooperation with Ritsumeikan University, Chiba University, University of Montpellier and Theoretical Physics at LiU.

Novel nitride alloys and nanostructures

Alloying group III A and III B nitrides offers a pathway to create new functionalities and engineer the optical and electronic properties of nitrides. Recently, ScAl(Ga)N and YAl(Ga,In)N have received significant interest due to their attractive optoelectronic and piezoelectric properties, and their compatibility with GaN technology. However, very little is known about these materials and their potential in future photonic and electronic devices needs to be established. To address these demands we study the optical properties, dielectric functions and phonons in YAlN, ScAlN and related nanostructures.

Research financed by Linköping University and FCT, Portugal

Cooperation with Thin Film Physics and University of Nebraska-Lincoln

THz ellipsometry and Optical Hall effect

We aim at developing unique THz ellipsometry and magneto-ellipsometry (THz Optical Hall effect) methodologies. These novel techniques will make it possible to explore electronic, transport and magnetic properties and phenomena in e.g, semiconductors, nanomaterials, organic materials, which cannot be assessed by other means. In short term perspective we expect to develop understanding and create knowledge about the mechanisms that control the free-charge carrier properties of epitaxial graphene and III-nitride heterostructures in order to achieve their desired transport properties. As a result of our research we will foster progress in novel technologies and functionalities based on epitaxial graphene and III-nitrides, such as THz electronics, power electronics, highly efficient solid state lighting and photovoltaics. Our ambition is to establish a unique center for THz and magneto-optic ellipsometry at Linköping.

Research financed by SSF, ÅForsk and VINNOVA

Cooperation with J. A. Woollam Co and CMO at University of Nebraska-Lincoln

Responsible for this page: Vanya Darakchieva
Last updated: 06/10/15