Epitaxy of hexagonal SiGe heterostructures
Hexagonal silicon-germanium (hex-SiGe) alloys have recently been confirmed to have a direct bandgap, with light emission between 3.4 and 1.8 micrometer. An efficient light source in this wavelength range, compatible with CMOS technology, is highly sought-after.
Applications could be in sensing or data communication. Proposed optical interconnects for data communication promise a reduced energy consumption of computer chips, while simultaneously increasing their performance.
Promising material
Hex-SiGe alloys are a promising material system for light emission. However, the growth of SiGe in the metastable hexagonal crystal structure has certain challenges, which are discussed in Peeters’ thesis.
One of the major results of this thesis is the realization of quantum wells. These are structures in which electrons are localized in specifically designed layers, only a few nm in width.
Localize in quantum wells
Moreover, Peeters demonstrated that holes, i.e. missing electrons, localize in these quantum wells. These heterostructures where both charge carriers localize in the same layer are known as type-I quantum wells.
Similar quantum wells are already used in other material systems to increase the performance of lasers, and they may eventually be used to fabricate lasers of hex-SiGe as well.
In short, Peeters thesis addresses multiple aspects that are important in the epitaxy of hex-SiGe crystals and its heterostructures, and it paves the way toward light-emitting devices of hex-SiGe.
Title of PhD thesis: . Supervisors: Erik Bakkers, Marcel Verheijen, and Jos Haverkort.