Our research focuses on silicon, silicon-germanium and silicon carbide
semiconductors. The research programme is process and materials oriented but
also includes devices and device physics. We conduct both fundamental and
applied research. We study how defects and impurity atoms influence the material
and electronic properties of semiconductors, and how this affects their use in
modern devices. We try to \"look inside\" operating devices to study current
flows, electrons and holes concentrations, or to measure local temperatures.
Silicon carbide (SiC) is a \"new\" semiconductor material with unique properties.
It has a high bandgap and very high \"critical field strength\". It can be used in
devices at very high temperatures and at very high voltages. It has therefore
attracted considerable interest in the electric power industry. We are studying
defects and impurities and seeing how they diffuse in the material. We are
developing computer simulation tools to calculate the performance of devices,
and a high voltage diode to investigate the voltage tolerance of materials. We
have also developed a new optical technique to \"see\" charge-carriers \"inside\"
operating silicon carbide devices.
The study of defects and diffusion in semiconductors – particularly in
connection with ion implantation – has a long tradition in this laboratory. In
particular the characterisation of transient diffusion has aroused much interest
lately. The phenomenon imposes severe limitations for achieving ultra-shallow pn-junctions
– a difficult problem in modern VSLI technology.
A new and very exciting project is in the field of nano-structures in silicon.
Working on this very small scale, quantum physics comes into play and silicon
acquires new characteristics – one may talk about silicon nanocrystals or
quantum dots. As a result silicon becomes optically active; this could be used
for light-emitting devices such as in displays. We are also using electron beam
lithography to fabricate nano-structures, which can subsequently be made even
smaller by means of oxidation or electrochemical etching. The goal is silicon
handcrafting at a nanometre level.
At the micrometre level, three-dimensional structures can be built by means of
deep etching of silicon (Deep Reactive Ion Etching), which we have used to make
a high sensitivity imaging X-ray detector (for dental applications). A further
development here is electro-chemical etching where pillars and pores can be
produced with very large aspect (depth-to-width) ratios.
Company Details
Material Physics, Oscar Tjernberg
Functional Materials, Mamoun Muhammed
Semiconductor Materials, Sebastian Lourdudoss
Devices and Circuits, Mikael Östling
Photonics, Urban Westergren
Quantum Electronics and Optics, Urban... more
