Layer-by-layer thermal conductivities of the Group III nitride films in blue/green light emitting diodes

Thermal conductivities (k) of the individual layers of a GaN-based light emitting diode(LED) were measured along [0001] using the 3-omega method from 100-400 K. Base layers of AlN,GaN, and InGaN,grown by organometallic vapor phase epitaxy on SiC, have effective kmuch lower than bulk values. The 100 nm thick AlN layer has k  = 0.93 ± 0.16 W/mK at 300 K, which is suppressed >100 times relative to bulk AlN. Transmission electron microscope images revealed high dislocation densities (4 × 10¹⁰ cm⁻²) within AlN and a severely defective AlN-SiC interface that cause additional phonon scattering. Resultant thermal resistances degrade LED performance and lifetime making layer-by-layer k, a critical design metric for LEDs.