PhD Studentship: Carrier transport modelling in group-IV SiGeSn quantum well semiconductor lasers

Funding

EPSRC Doctoral Training Partnership Studentship offering the award of fees, together with a tax-free maintenance grant of £19,237 per year for 3.5 years.  Training and support will also be provided.

Lead Supervisor’s full name and email address

Dr Zoran Ikonic – [email protected]

Co-supervisor name(s)

Professor Robert Kelsall – [email protected]

Dr Dragan Indjin – [email protected]

Project summary 

Large-scale optoelectronics integration is limited by inability of conventional group-IV semiconductors (silicon and germanium) to be efficient light emitters, because of their indirect bandgap. In recent years a big advance has been made in this direction by successful demonstration of lasing in germanium-tin alloys, which can be direct bandgap semiconductors. This first working group-IV laser was optically pumped, and had a limited operation temperature, only up to T < 90 K. Further developments have increased the maximum operating temperature up to 270 K with optical pumping, and electrically pumped lasing up to 110K has also been demonstrated. Direct-bandgap group IV materials may therefore represent a pathway towards monolithic integration of group-IV based photonics and CMOS technology. Important further developments on this route would be electrically pumped laser operating at room temperature. A way forward could be to use multiple quantum well (MQW) structures, which have improved very much the performance of III-V based lasers.

In this project the carrier transport in MQW laser structures will be considered, to describe the carrier trapping in quantum wells, or escape into other wells or into continuum. The aim will be to achieve a reasonably homogeneous distribution of electrons and holes across the MQW structure. The methodology is described in the literature on III-V semiconductor based MQW lasers, but will here be used for group-IV materials. The electronic structure of SiGeSn based MQWs, necessary for transport modelling, will be calculated using the already developed codes. The overall target would be to find good choices for the wells and barriers, or even their shapes, to deliver a good carrier distribution, accounting for practical constraints in the material composition of SiGeSn alloy which can actually be grown. Based on that, structures which are optimal, or at least good enough to be prospective, will be designed for laser operation at room temperature.

Entry requirements plus any necessary or desired background

Masters degree in Electronic Engineering or Physics

Subject Area

Electronic & Electrical Engineering, Semiconductor optoelectronics