Probing nanoscale thermal transport with cathodoluminescence thermometry

TL;DR

This paper introduces novel electron-beam based methods for high-resolution, in-situ measurement of thermal conductivity in semiconductor nanostructures, overcoming previous limitations of spatial resolution and fabrication complexity.

Contribution

It presents a new cathodoluminescence thermometry technique combined with steady-state and pulsed electron beam methods to measure nanoscale thermal conductivities.

Findings

Thermal conductivities of GaN nanowires measured between 19-68 W/m*K.

Methods agree within error where comparable.

Enables rapid, high-resolution thermal property measurements in nanodevices.

Abstract

Thermal properties have an outsized impact on efficiency and sensitivity of devices with nanoscale structures, such as in integrated electronic circuits. A number of thermal conductivity measurements for semiconductor nanostructures exist, but are hindered by the diffraction limit of light, the need for transducer layers, the slow-scan rate of probes, ultra-thin sample requirements, or extensive fabrication. Here, we overcome these limitations by extracting temperature from measurements of bandgap cathodoluminescence in GaN nanowires with spatial resolution limited by the electron cascade, and use this to determine thermal conductivities in the range of 19-68 W/m*K in three new ways. The electron beam acts simultaneously as a temperature probe and as a controlled delta-function-like heat source to measure thermal conductivities using steady-state methods, and we introduce a frequency-domain method using pulsed electron beam excitation. The different thermal conductivity measurements we explore agree within error where comparable. Our results provide novel methods of measuring thermal properties that allow for rapid, in-situ, high-resolution measurements of integrated circuits and semiconductor nanodevices, and open the door for electron-beam based nanoscale phonon transport studies.