Multiwavelength Emission from InGaN/GaN MQW Truncated Pyramids Grown on a GaN Dodecagonal Pyramid Template

InGaN/GaN multiple quantum well (MQW) truncated pyramids with multiwavelength emission were successfully fabricated by means of a simple and low-cost regrowth method on a GaN dodecagonal pyramid template. This template obtained by H3PO4 etching the N-ploar GaN bulk material showed six pairs of alternating Ga-polar and N-polar edges. The luminescence properties of the InGaN/GaN MQW structure were investigated by both photoluminescence (PL) and spatially resolved cathodoluminescence (CL) with scanning electron microscopy (SEM) measurements. It was found that the emission wavelength of InGaN/GaN MQWs was very broad and red-shifted from the bottom to the top of the pyramid. The high emission intensity around 420–480 nm originated from the edges and sidewall of the pyramids. Additionally, longer emissions from the (1̅1̅22̅) facet MQWs and the periphery of the micron-sized truncated pyramid (TP) were observed, consisting of multiple peaks ranging from 460 to 540 nm. Furthermore, the growth model of MQWs on GaN dodecagonal pyramid templates was established to explain the nonuniformity in distribution and flower- or star-like pattern formation on pyramid sidewalls. It took into account the combined effects of strain distribution at the InGaN/GaN heterostructure interface, different incorporation rates of Ga and In atoms at Ga- or N-polar surfaces, and different diffusion lengths of Ga and In adatoms on GaN template lateral facets. The proposed structure, due to its low-cost and easy fabrication process, could be a promising candidate for highly efficient broadband visible light-emitting devices.