Designing the Electronic Properties of PbSe Nanowires for Optoelectronic Devices

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Technical Description: Semiconductor nanowires allow the interrogation of unique materials physics that arises in one-dimensional materials and the exploitation of their properties for a wide range of applications. PbSe is a unique materials system to probe in one-dimension: it has large electron, hole, and exciton Bohr radii, giving rise to strong quantum confinement in small-diameter nanowires, and it has a large dielectric constant compared to host matrices, leading to strong dielectric confinement. Confinement effects in nanowires dramatically alter their electronic structure as well as carrier statistics, dynamics, and transport. The goal of this project is to understand the influences of strong quantum and dielectric confinement on the electronic properties of PbSe nanowires and their importance in designing nanowire p-n junctions in particular for mid-infrared photodetectors and for photovoltaics. Colloidal PbSe nanowires, tunable from 4 to 20 nm in diameter, are synthesized and integrated as single nanowires and nanowire arrays in devices embedded in different dielectric environments. After nanowire integration, routes to substitutionally and remotely dope nanowires are applied to understand doping and its efficiency in these one-dimensional, strongly quantum and dielectrically confined semiconductors and to controllably define p-n junctions within high-mobility nanowires. Electrical and optoelectronic measurements are used to probe doping efficiency and charge injection and transport in n- and p-doped PbSe building blocks and the electrostatics, carrier diffusion, and performance of p-n junctions to design high-efficiency optoelectronic devices.Non-technical Description: Semiconductor devices are constructed by defining junctions between n- and p-type doped regions, to introduce excess electrons and holes, respectively. In one-dimensional materials, the p-n junctions are affected by their small diameter as well as by contrast between the dielectric constant of the nanowires and their surrounding materials. This project explores the impact of one dimension in a semiconductor material where the effects of small size and dielectric contrast are high. These nanowires are promising for high-efficiency mid-infrared photodetectors and for photovoltaics. This project provides an interdisciplinary research experience for undergraduate and graduate students. The PI and students are sharing the science of one-dimensional, nanoscale materials and their technologies through student coursework and outreach activities to engage K-12 students, teachers, and the general public.