Remote temperature mapping of high-power InGaN/GaN MQW flip-chip design LEDs

Abstract

We report on the study of heat 2D-distribution in InGaN LEDs with the stress made on local device overheating and temperature gradients inside the structure. The MQW InGaN/GaN/sapphire blue LEDs are designed as bottom emitting devices where light escapes the structure through the transparent GaN current spreading layer and sapphire substrate, whereas the LED structure with high-reflectivity Ni/Ag p-contact is bonded to the thermally conductive Si submount by a flip-chip method. The measurements are performed with an IR microscope operating in a time-resolved mode (3-5 um spectral range, <20 µm spatial and 10 µs temporal resolution), while scanning a heat emission map through a transparent sapphire substrate. We show how current crowding (which is difficult to avoid) causes a local hot region near the ncontact pads and affects the performance of the device at a high injection level.

Enhanced optical output of InGaN/GaN near-ultraviolet light-emitting diodes by localized surface plasmon of colloidal silver nanoparticles

“…Then, a transparent current spreading layer (indium tin oxide, 150 nm), n-and p-contact layer of Cr (50 nm)/Au (150 nm) were deposited on the LED devices (300×300 μm 2 ) using an e-beam evaporator as shown in figure 1(d). [33,34]. Therefore, the distance between Ag NPs (50-200 nm) embedded in p-GaN is sufficient to prevent agglomeration of Ag NPs by heat generated during LED operation.…”

The effect of current crowding on the heat and light pattern in high-power AlGaAs light emitting diodes

“…12,13 The catastrophic degradation of blue InGaN quantum well LEDs also occurs in the CC region. 14 General trends in commercial AlGaAs-based LEDs have been toward a higher output, a high quality light beam, and a longer operation time. Therefore, the attempts to minimize the CC effect seem to be of the most urgency.…”

Highly efficient GaN vertical light emitting diode on metal alloy substrate from near UV to green color for solid state lighting application

“…This makes the thermal management tough and costly when the high power output is required. The second one is the severe current crowding resulted from the lateral current conduction 3,4 . The progress of solid state lighting is impeded by these inherent restrictions, and demands an all-new GaN LED structure, which can surpass the original one and meet the minimum performance required for Solid State Lighting.…”