High Efficiency Diode Lasers based on Nanopatterned Quantum Dot Active Regions

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"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."Quantum dot (QD) active regions hold potential for realizing extremely high performance semiconductor diode lasers. Unfortunately, these unique features of ideal QD active layers have not been fully realized to date. The most successful approach to date of forming QD's are self-assembly under the Stranski-Krastanow (SK) growth mode. However, this approach results in a relatively large distribution of QD sizes, leading to significant inhomogeneous broadening of the spectral gain. SK QDs inherently form on top of a two-dimensional 'wetting layer', leading to weak electron and hole confinement to the QD, which results in low gain saturation. Here, we employ dense nanoscale diblock copolymer lithography-based nanofabrication which eliminates the wetting layer states and improves QD size uniformity.Intellectual Merit:The intellectual merit is that these structures will allow for the first time the study of the optical gain characteristics of near ideal (i.e. complete 3D quantum confinement) QD active regions, improving understanding carrier recombination mechanisms, optical gain, and radiative efficiency of QDs. The broad impact of such studies encompasses the first realization of compact diode laser sources with power conversion efficiencies in excess of 80%, drastically reducing power consumption for high output power applications. Broader Impacts:The educational broad impact is that graduate students will learn all aspects of optoelectronic device engineering, from design to fabrication and characterization. Students will have access to state-of-the-art crystal growth facilities at UW-Madison and extensive material characterization techniques to assess the optical and structural quality of the quantum dots.