Examination of the Ion Beam Response of III-V Semiconductor Substrates.

Abstract

This work examines the response of the III-V materials to ion beam irradiation in a series of four experimental studies and describes the observed results in terms of the fundamental materials processes and properties that control ion-induced change in those compounds. Two studies investigate the use of Ga+ focused ion beam (FIB) irradiation of III-V substrate materials to create nanostructures. In the first, the creation of FIB induced group III nanodots on GaAs, InP, InAs, and AlAs is studied. The analysis of those results in terms of basic material properties and a simple nanodot growth model represents the first unified investigation of the fundamental processes that drive the nanodot forming behavior of the III-V compounds. The second nanostructure formation study reports the discovery and characterization of unique spike-like InAs nanostructures, termed “nanospikes,” which may be useful for nanoscale electronic or thermoelectric applications. A novel method for controlling nanospike formation using InAs/InP heterostructures and film pre-patterning is developed, and the electrical properties of these ion erosion created nanostructures are characterized by in-situ TEM nanoprobe testing in a first-of-its-kind examination. The two remaining studies examine methods for using ion beam modification of III-V substrates to accommodate lattice-mismatched film growth with improved film properties. The first examines the effects of film growth on a wide range of different FIB created 3-D substrate patterns, and finds that 3-D surface features and patterns significantly alter film morphology and that growth on or near FIB irradiated regions does not improve film threading defect density. The second substrate modification study examines broad beam ion pre-implantation of GaAs wafers before InGaAs film growth, and is the first reported study of III-V substrate pre-implantation. Ar+ pre-implantation was found to enhance the formation of threading defects in InGaAs films and so improve their roughness and degree of relaxation. This effect, combined with a threading dislocation filtering structure, is anticipated to produce high quality buffers for lattice-mismatched film growth.Ph.D.Materials Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/91437/1/kgrosskl_1.pd