GOALI: Defect Formation and Phase Transitions in 2-5 Micron GaInAsSb Semiconductor Quaternary Alloys versus Ga(In)Sb/InAs Short Period Superlattices

University Of Iowa, Iowa City IA

Investigators

Abstract

Technical: This project addresses phase transitions and defect formation in antimonide III-V materials, including direct gap quaternary materials GaInAsSb and InAs/Ga(In)Sb superlattices having bandgaps covering the 2-5 micron spectral range. These materials are expected to be of growing importance to infrared optoelectronic devices, including photodiode detectors, light emitting diodes, laser diodes, and thermophotovoltaics. However, GaInAsSb alloys grown under thermodynamic equilibrium conditions unstrained on GaSb substrates have immiscibility regions in the alloy phase space according to thermodynamic calculations, potentially limiting stability of desired compositions. This project will study and map out the influence of strain and growth kinetics on quantum well GaInAsSb alloys across the thermodynamic immiscibility region. Imaging techniques will be used to study characteristic defect formation, phase separation, and spinodal decomposition. Photoluminescence, absorption and optical lifetime measurements will be used to correlate morphology and optical properties, including radiative and nonradiative decay processes. Alternative materials to GaInAsSb alloys with direct gaps covering the 2-5 micron wavelength region, short-period, type-II InAs/Ga(In)Sb superlattices (T2SL) will be addressed as well. They have several characteristics in common with GaInAsSb alloys, including common elemental composition, as well as GaInAsSb regions at interfaces and in layers due to intermixing. The project aims to advance state-of-the-art understanding of crystal growth and material properties of GaInAsSb alloys and InAs/Ga(In)Sb superlattices, and allows testing at both research grade MBE reactors at U. IA as well as industrial grade MBE reactors at IQE. New, comprehensive data will be obtained on comparisons between measured and calculated properties of these materials, with theoretical calculations provided by ASL Analytical. Non-technical: This GOALI (Grant Opportunities for Liaison with Industry) project addresses basic research issues in a topical area of materials science with high technological relevance. Collaborative links between the University of Iowa academic group and industrial partners, IQE and ASL Analytical are synergistic, and provide advantageous opportunities for scientific, technological, and educational impacts. The PI will recruit and hire a new graduate and undergraduate student to work on the project and advise the graduate student through the completion of his or her PhD. The graduate student will get research experience working both in academic (U. IA) and industrial (IQE, ASL) environments. The PI will reinvigorate a U. IA Physics and Astronomy outreach program called "Family Adventures in Science," featuring a series of lectures on a theme by different faculty members to the public; one of the themes will be semiconductors. Additionally, the PI will propose a one credit seminar for first year students on approaches to science through study of several famous scientists.