title: Simultaneous Thermoelectric and Optoelectronic Characterization of Individual Nanowires.
abstract: Semiconducting nanowires have been explored for a number of applications in optoelectronics such as photodetectors and solar cells. Currently, there is ample interest in identifying the mechanisms that lead to photoresponse in nanowires in order to improve and optimize performance. However, distinguishing among the different mechanisms, including photovoltaic, photothermoelectric, photoemission, bolometric, and photoconductive, is often difficult using purely optoelectronic measurements. In this work, we present an approach for performing combined and simultaneous thermoelectric and optoelectronic measurements on the same individual nanowire. We apply the approach to GaN/AlGaN core/shell and GaN/AlGaN/GaN core/shell/shell nanowires and demonstrate the photothermoelectric nature of the photocurrent observed at the electrical contacts at zero bias, for above- and below-bandgap illumination. Furthermore, the approach allows for the experimental determination of the temperature rise due to laser illumination, which is often obtained indirectly through modeling. We also show that under bias, both above- and below-bandgap illumination leads to a photoresponse in the channel with signatures of persistent photoconductivity due to photogating. Finally, we reveal the concomitant presence of photothermoelectric and photogating phenomena at the contacts in scanning photocurrent microscopy under bias by using their different temporal response. Our approach is applicable to a broad range of nanomaterials to elucidate their fundamental optoelectronic and thermoelectric properties.
authors.affiliation: Sandia National Laboratories , Livermore, California 94551, United States.
authors.forename: François
authors.initials: F
authors.lastname: Léonard
authors.affiliation: Department of Chemical & Materials Engineering, New Mexico State University , Las Cruces, New Mexico 88003, United States.
authors.forename: Erdong
authors.initials: E
authors.lastname: Song
authors.affiliation: Sandia National Laboratories , Albuquerque, New Mexico 87123, United States.
authors.forename: Qiming
authors.initials: Q
authors.lastname: Li
authors.affiliation: Center for Integrated Nanotechnologies, Sandia National Laboratories , Albuquerque, New Mexico 87185, United States.
authors.forename: Brian
authors.initials: B
authors.lastname: Swartzentruber
authors.affiliation: Department of Chemical & Materials Engineering, New Mexico State University , Las Cruces, New Mexico 88003, United States.
authors.forename: Julio A
authors.initials: JA
authors.lastname: Martinez
authors.affiliation: Sandia National Laboratories , Albuquerque, New Mexico 87123, United States.
authors.forename: George T
authors.initials: GT
authors.lastname: Wang
keywords: GaN; GaN/AlGaN; Nanowires; photocurrent; photogating; thermoelectric