III-Nitrides for next generation rf and power electronics

The physical properties of the III-N semiconductors make them ideal for reducing energy consumption, improving performance and reducing costs in high power and high frequency electronic systems. However, substantial development of both material and devices is needed to fully exploit the advantages of the III-N technology and to make it commercially viable.We have identified several scientific and technological challenges which must be addressed to exploit the full potential of III-Nitrides with applications in the next generation of wireless communication, sensing, and power infrastructures. The research is in the heart of a the newly established competence center C3NiT-Janzén, which has the mission to perform and transfer research results on III-Nitride high frequency and high-power technology directly exploitable by industrial partners at different levels in the supply-chain. More specifically my research includes optimization of epitaxial design of GaN and AlGaN device structures on SiC, GaN and AlN substrates for microwave and power electronics. This activity covers the actual growth of the device structures with the main aim to minimize defect densities (dislocations and background impurities), and the design of the epi-stack targeting different functionalities, e.g. power amplification, noise, and flicker-noise, switch losses, device design, etc. Further research activities include studying, understanding and optimizing n- and p-type doping in Al,In(Ga)N epitaxial layers and 2DEG in heterostructures by employing unique THz spectroscopic ellipsometry and optical Hall effect methods at the THz Materials Analysis Center.

Research financed by VR, VINNOVA and SSF

Cooperation with SweGaN, Saab, ABB, Ericsson, On Semiconductor, Ericsson, Gotmic, UMS, Epiluvac, FMV, Chalmers University and Lund University

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