Multiwavelength-emitting InGaN quantum wells on convex-lens-shaped GaN microstructures

Abstract

We fabricated InGaN quantum wells (QWs) on GaN microlens structures by employing a thermal reflow method. The peak emission wavelengths shift from ~490 nm on the top of the microstructure to ~400 nm on the bottom. This variation is attributed to the In composition distribution caused by the continuously changing off-angles from the (0001) plane. The obtained results suggest that not only stable planes exposed in microstructures by selective area growth technique but also unstable planes can be useful for InGaN-based microstructures with multiwavelength emission properties.

InGaN-based LEDs on convex lens-shaped GaN arrays toward multiwavelength light emitters

“…[5][6][7][8][9][10][11][12][13][14][15] Recently, attempts using substrates with local off-angle patterning have been proposed for InGaN-based multiwavelength light emitters. [16][17][18][19][20][21] Well-designed 3D shapes of photoresists are transferred to GaN surfaces, forming local off-angle distributions. A remarkable feature of this method is that not only stable planes exposed in the 3D structures by SAG but also unstable planes can be used.…”

“…Very recently, we have proposed InGaN QWs on convex lens-shaped GaN microstructures using a thermal reflow method. 21) The microlens shape exposes continuously changing off-angles in a single microstructure. Hence, a single microstructure displays a multiwavelength emission property.…”

“…Detailed procedures are explained elsewhere. 21,22) The disk photoresist in this study had a 20 μm diameter, and the disk shape was transformed into a convex lens shape by the thermal reflow method. Then, inductively coupled plasma reactive ion etching (ICP-RIE) transferred the convex lens shape of the photoresist to the GaN surfaces.…”

“…It should be noted that the convex lens-like shapes are preserved after the regrowth of the GaN underlayers and InGaN QWs (hereafter, these structures without p-GaN layers are referred to as microlens QWs). 21) Thus, the (0001) facets form during the growth of the p-GaN layers.…”

“…2(b). The height profile of the microlens QWs 21) is also plotted to demonstrate the 3D shape evolution during the p-GaN growth. Here, the height profile for the LED structure is shifted upward to highlight the essential height relation.…”