(Georgia Institute of Technology, 2005-08)
Christensen, Adam; Doolittle, William Alan; Graham, Samuel
The heat dissipation in GaN devices grown on low
thermal conductivity lithium gallate (LGO) substrates was investigated.
The thermal conductivity of single-crystal LGO was measured
utilizing the 3ω technique for temperatures ranging from
100 K–500 K. For the GaN layer, the thermal conductivity was estimated
using a phonon transport model which included dislocation
density and temperature dependence. These data were then used
in a finite element program to determine the thermal behavior of
a heterojunction field-effect transistor. Based on a maximum junction
temperature of 500 K, it was found that devices with a power
dissipation of 1W/mm were possible if the primary heat dissipation
path was through the low thermal conductivity substrate. However,
in using a front side cooling scheme, results suggest that it may be
possible to develop devices with power dissipation in the range of
10 W/mm.