A novel method for the thermal analysis of GaN/AlGaN back-illuminated high power UV LEDs

Abstract

We report a novel method for the thermal analysis of high-power multi-quantum well GaN/AlGaN UV LEDs of λ ∼ 330 nm. 3D modeling and simulations of chip-on-plate (COP) have been investigated for the packaging of UV LEDs. Steady state thermal analysis of COP packaged devices were carried out using finite element method (FEM). Different heat sinks’ designs such as plate-fins, and pin-fins were modeled to determine device junction temperatures (Tj). We also employed thermal resistance circuit (TRC) model to determine the Tj considering both conductive and convective methods of heat transfer. Results were in good agreement both for the FEM and TRC models. For the fine plate-fin dense and the less-dense large-fins heat sinks, calculated Tj values were ∼37 °C, and ∼46 °C for a corresponding operating power of ∼1.5 W, respectively. On other hand, similar power level junction temperatures of 33 °C and 41 °C were determined respectively for high- and low-density pin-fins heat sinks. Furthermore, thermal flux analysis of these heat sinks was also performed. A comparative study of on–substrate un-packaged and two different (COP) packaged devices was also performed. It was found that our COP based packaged devices are thermally more stable with improved photoluminescence (PL) intensity. As much as around 30% enhancement in the PL intensity of the packaged devices along with a noticeable decrease in the red-shift (about 7 nm) of the spectrum was determined.