Gallium nitride illuminated

Promotor: Prof. Benoit Bakeroot (CMST, ELIS), Prof. Dirk Poelman (Lumilab, Vastestofwetenschappen)

Guidance: Prof. Benoit Bakeroot, Lisa Martin

Inlichtingen: tel. 09/264.43.42 of contacteer rechtstreeks een betrokken persoon (de contactgegevens opvragen door op de naam te klikken)

Key words:
semiconductor physics, GaN, luminescence

Probleemstelling:

It is estimated that more than sixty percent of the electricity produced worldwide passes through one or more semiconductor devices (mostly in voltage convertors).  The efficiency at which the electronic circuit – and, thus, the devices – convert electrical energy has an enormous impact on the worldwide consumption of electricity. Up to this date, the majority of these devices are still made of silicon.  Yet, a radical improvement of the conversion efficiency can only be achieved when using other semiconductors.  From a theoretical point of view, wide band gap semiconductors are much more suited for high voltage applications.  Both silicon carbide (SiC) and gallium nitride (GaN) have good credentials: both have a band gap well above 3.0 eV which results in critical electric fields about ten times that of silicon, both have high mobilities and saturation velocities, and both have a relatively good thermal conductivity.  Of course, besides these theoretical considerations there are economical ones and the technology to make devices in those semiconductors must be cost-effective.  GaN-on-Si is a very promising technology as one can grow GaN on large silicon wafers (8 inch).  Unfortunately, one of the main challenges for the technology remains the reduction of the number of defects in the GaN.

Doelstelling:

After the student gets acquainted with gallium nitride and its most important properties, a commercial software tool (Synopsys’ Technology Computer Aided Design or TCAD) will be introduced.  This TCAD tool numerically solves the Poisson and drift-diffusion equations using finite-element methods and enables a further study of GaN devices. The research group CMST (Prof. B. Bakeroot) has a long-standing experience in simulating semiconductor devices and will guide this part of the thesis.  Another important part of this thesis consists of both photoluminescence and cathodoluminescence measurements in electron microscope.  The samples are provide by Imec through CMST, which is an Imec associated lab.  The luminescence measurements take place in the Sterre (S1) under the supervision of Prof. D. Poelman (Lumilab, Faculty of Sciences).  The goal is to study the defects in the gallium nitride samples and to extract as much as possible the electrical properties.  A final stage in the thesis would then be to couple back the experimental findings to the TCAD simulations in order to get a better insight in the working principles of the GaN devices.