Comparison Of Growth Interruption And Temperature Variation Impact On Emission Efficiency In Blue Ingan/Gan Mqws

Pulsed growth, i.e. the MOCVD growth method, when the metal precursors are delivered with interruptions, allows increasing the internal quantum efficiency (IQE) of InGaN multiple quantum well (MQW) structures. On the other hand, similar results are achieved by increasing the growth temperature. In this work, we analyze the physical mechanisms behind the IQE improvement in differently grown QWs at low and high carrier densities. At low excitations, the In0.1Ga0.9N/GaN MQW structures grown at 800 and 815 degrees C exhibited the PL efficiency of 4% and 6%, respectively. At high excitations, the benefit of higher growth temperature disappeared: peak IQE at the droop onset was similar to 34% in all structures. Moreover, the structure grown at 815 degrees C had lower than intended indium content (9% instead of 10%) and QW width (3.5 nm instead of 4.0 nm). The pulse-grown structures, while very sensitive to interruption duration, provided peak IQE up to 40% without decline in structural quality. From the provided photoluminescence, carrier lifetime and diffusion coefficient data we speculate that higher growth temperature leads to lower point defect density, which increases IQE at low excitations, but becomes saturated at high excitations. Meanwhile, the pulsed growth mainly affects the localizing potential, which governs carrier recombination pathways.