Precise Characterization and Investigation of Laser Cooling in III-V Compound Semiconductors
The physics and engineering issues associated with laser cooling of III-V compound semiconductors, in particular GaAs double heterostructures (DHS), are theoretically and experimentally investigated. This research addresses the key concepts of external quantum efficiency (EQE) and parasitic background absorption in a semiconductor laser cooler. The external quantum efficiency describes how well recombination radiation is removed from the cooling device and is precisely measured by All-optical Scanning Laser Calorimetry (ASLC). Using this technique, a record external quantum efficiency of 99.5% has been obtained with a GaAs laser cooler held at 100 K. However, high background absorption has hindered the observation of net cooling. Pulsed Power-dependent photoluminescence measurement (Pulsed PDPL) is proved to be an efficient way to determine the external quantum efficiency and screen the sample quality before device fabrication. We observe lateral lasing effect in both double heterostructure and quantum well semiconductors and show that the phenomenon can be explained by the effect of bandgap renormalization due to Coulomb screening. The knowledge gained in the research described here is essential toward the realization of net laser cooling in III-V compound semiconductors in the future.
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