Quantitative heat dissipation in GaN nanowire devices Yi Gu , Washington State University, DMR 0845007

1. (a) (b) (c) Metal electrode Quantitative heat dissipation in GaNnanowire devicesYi Gu, Washington State University, DMR 0845007 Wheatstone Bridge Circuit Pt wire junction ~ 100 – 200 nm (a) Schematics of the scanning thermal microscopy; (b) maps of the Wheatstone bridge voltage of an operating GaNnanowire device; (c) line profile (black solid line) of the normalized temperature along a GaNnanowire fitted by a one-dimensional heat diffusion model (dashed red line). Carrier transport in semiconductors reflects several fundamental processes such as carrier-phonon interactions. At low electric fields, acoustic phonons dominate the carrier-phonon scattering. One of the manifestations of this interaction is the Joule heat generation, which can provide insight into the carrier-phonon interactions and phonon transport characteristics. Here, we developed an approach combining scanning thermal microscopy (SThM) and spatially resolved Raman spectroscopy, which enables quantitative characterizations of Joule heat generation and dissipation in single nanowires. Our results suggest that acoustic phonon transport in GaNnanowires with diameters ~ 40 – 60 nm, where phonon confinement effects are expected, is diffusive in nature at room temperature. We have also quantitatively determined the nanowire thermal conductivity and nanowire-substrate/electrode interface thermal resistances. These results demonstrate the feasibility to directly and quantitatively probe nanoscale carrier-phonon interactions manifested by heat generation and dissipation in individual nanowires. From a practical perspective, the parameters obtained are central to the development of efficient thermal management schemes for nanoscale devices.

2. Education and Outreach Activities Yi Gu, Washington State University, DMR 0845007 Robert Dawson, an undergraduate physics major at WSU, uses a confocal Raman microscope in PI’s lab to study phonon properties and carrier-phonon interactions in single nanowires. AfsoonSoudi (right), a Ph.D student in PI’s group, gives a presentation of research efforts and a tour of PI’s lab to Colville High School students.