Morphological improvement and elimination of V-pits from long-wavelength all-InGaN based uLEDs grown by MOCVD on compliant substrates

We examine the MOCVD growth conditions on c-plane semi-relaxed InGaN substrates necessary for morphological improvement, defect reduction, and elimination of V-pits during epitaxy prior to the active region growth. V-pit defects can propagate through the crystal as epitaxy continues, causing serious morphological degradation. These defects may also be a source of leakage current if they form a low-resistance path through p-n junction. By employing an InGaN/GaN periodic structure, thick base layers can be grown with the morphology improving as the epitaxy proceeds, allowing for high quality layers to be achieved. High temperature (HT) GaN interlayers in the InGaN/GaN base layer structure then continue to reduce defects significantly, notably eliminating the V-pit type defect, and significantly improving growth morphology. Resulting microLEDs on these improved base layers exhibit a nearly three order of magnitude reduction in leakage current density at 1V, far below the μLED turn-on threshold, and significantly lower dynamic resistance. This result indicates the reduction in base layer defects and layer morphology improvement results in significant improvement in electrical performance and enables production of viable LEDs.