Laser cooling of a semiconductor has been an elusive but highly desirable goal for several years. Although it is
theoretically possible, tedious and often time-consuming sample preparation, processing and testing has slowed
the progress on the experimental end. The work presented here focuses on a new approach to the first step, the
growth of high quality starting samples by molecular beam epitaxy (MBE).
MBE is believed to have an inherent advantage over chemical vapor deposition techniques since typically
material with higher purity can be grown by MBE, thereby reducing the chance for parasitic absorption and nonradiative
recombinations to occur. Additionally, with MBE very precise control over interfaces is possible,
where a significant portion of the non-radiative traps are usually located. The most promising material for laser
cooling is the binary compound GaAs. The lattice-matched material Ga0.515In0.485P is chosen for passivating the
surface as it has shown much longer radiative lifetimes in GaAs than, for example, AlxGa1-xAs. The present
study focuses on growth optimization of Ga0.515In0.485P/GaAs/Ga0.515In0.485P heterostructures and the influence of
growth conditions on sample suitability for laser cooling as measured by non-radiative lifetimes in GaAs. In
particular, parameters such as growth temperature, group V:III overpressure, substrate orientation, doping, and
interface composition on a monolayer length scale are varied and analyzed. The suitability of an optimized
sample for semiconductor laser cooling is discussed.