FRG: Morphological Electronic and Chemical Structure of Lattice-Mismatched III-V Heterojunctions

Ohio State University Research Foundation -Do Not Use, Columbus OH

Investigators

Abstract

This FRG project involves a cross-disciplinary group of PIs to explore underlying properties that dictate ultimate device-viability of lattice-mismatched heterojunctions. Lattice mismatch not only determines the growth morphology but also affects thermodynamic stability, creation of localized electronic states, and transport barriers at band edge discontinuities. Techniques for lattice matching lattice-mismatched materials can manipulate electronic and optical properties on an atomic scale. Control of these issues may remove constraints imposed by standard materials (e.g., GaAs and InP) on the functionality attainable from the full range of semiconductor materials. The perceived challenges are to achieve planar growth and thermal compatibility with simultaneous control of mechanical, chemical, and electronic structure. The inter-relationships between these properties and growth parameters must be understood at a fundamental level to achieve significantly greater utilization of lattice-mismatched heterostructures. The project strives to not only understand each set of properties, but also to discover how they result from specific variations in growth conditions. The approach incorporates (i) growth by molecular beam epitaxy (MBE), (ii) direct measurement of the atomic structure of the created materials, (iii) in-situ and ex-situ measurements of electronic, atomic-scale and optical properties, and (iv) theoretical calculations of electronic structure of the actual materials. A few model systems based on III-V compounds were chosen both for the technological importance of these material systems in advanced devices and as precisely controlled sample sets necessary to interpret the measurements and calculations. The project focus is primarily on InAlAs, InGaAs and InAsP mismatched heterostructures grown on InP, InGaP and InAlP grown on GaAs, and a few choice binary combinations of varying misfit to provide precisely controlled measurement data for correlation with theoretical calculations of properties. %%% The project addresses basic research issues in a topical area of materials science with high technological relevance. The project builds on recent advances in representative heterojunction systems, while adding new capabilities for characterizing electronic properties of mismatched films as they evolve with growth. The basic knowledge and understanding gained from the research is expected to contribute to improving semiconductor materials performance in current and future device and circuit applications. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. The multidisciplinary (materials science, electrical engineering, physics) nature of this FRG project offers unique educational opportunities for students to experience a teamwork-oriented research environment. ***