Collaborative Research: Study of Strain-Dependent Auger Recombination Processes in III-V Materials Using Membranes

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Nontechnical Description: Auger recombination is a process that degrades the performance of III-V materials for optoelectronic devices, ranging from lasers and light-emitting diodes, to solar cells and photodetectors. In particular, lasers emitting light in the mid-infrared region of the electromagnetic spectrum are impacted heavily by Auger recombination. Mid-infrared lasers are important for sensing, free-space communications, and medicine. This collaborative research project between the University of Colorado at Boulder and the University of Texas at Austin seeks to understand and control the Auger recombination process in III-V materials to ultimately enhance the performance of mid-infrared lasers. The research efforts are well integrated with the educational activities. The efforts include providing interdisciplinary research opportunities to graduate and undergraduate students, integrating research findings with college coursework, and K-12 outreach through optics-related modules.Technical Description: Strain can greatly reduce the negative effects of Auger recombination in quantum confined active regions in III-V materials. However, the fundamental understanding of the strain effects on the recombination processes has been hindered by the critical thickness limitations imposed by strain, complicating analysis and often necessitating unrealistic approximations. The collaborative project takes an orthogonal approach to the challenges associated with understanding and characterizing recombination processes by examining the active strained regions of the materials. Specifically, semiconductor membranes made of III-V materials are released from their host substrate and bonded to a flexible polymer. The membranes are biaxially strained by stretching the polymer substrate in two dimensions to mimic the effect of biaxial strain from lattice-mismatched growth. This permits strain-dependent studies of Auger recombination using ultrafast spectroscopy on a single sample, isolating the intrinsic effects of strain from those due to compositional change or growth kinetics. This study could shed light on the roles of Auger and other loss processes in III-V material systems, an ongoing 30+ year debate across the device and materials communities, and enable high-efficiency diode lasers and light-emitting diodes in visible regime.