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9 February 2009 MBE growth and characterization of semiconductor laser coolers
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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.
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Andreas Stintz, Chia-Yeh Li, Mansoor Sheik-Bahae, and Kevin J. Malloy "MBE growth and characterization of semiconductor laser coolers", Proc. SPIE 7228, Laser Refrigeration of Solids II, 722803 (9 February 2009);

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