Suppressing void defects in long wavelength semipolar (202¯1¯) InGaN quantum wells by growth rate optimization

Abstract

We report on void defect formation in ð2021Þ semipolar InGaN quantum wells (QWs) emitting in the green spectral region. Fluorescence and transmission electron microscopy studies indicate that this type of defect is associated with voids with f10 11g, f10 10g, and f000 1g side facets in the QW region. Systematic growth studies show that this defect can be effectively suppressed by reducing the growth rate for the active region. Green light-emitting diodes (LEDs) with reduced active region growth rate showed enhanced power and wavelength performance. The improved LED performance is attributed to the absence of void defects in the active region.

Near-field investigation of spatial variations of (202¯1¯) InGaN quantum well emission spectra

“…The most probable cause of the well band gap variation is nonuniformity of In distribution, since monolayer-thick well width variations in InGaN QWs would hardly provide large uniform islands, and strain fluctuations in thin 3 nm single QWs grown on homoepitaxial substrates are unlikely. Growth condition-dependent surface undulations along the a axis, along which our SNOM features appear, have been observed in ð20 2 1Þ InGaN QW structures 16 and ð20 21Þ InGaN epitaxial layers. 17 In ð20 21Þ QWs, surface morphology variations were found to correlate with spatial differences of PL properties.…”

“…25 Faceted void defects were also detected in high defect density semipolar InGaN QWs. 16 Thus, it is likely that the dual wavelength emission shown in Fig. 4 originates from areas containing QW segments of different orientations.…”

Molecular dynamics studies of defect formation during heteroepitaxial growth of InGaN alloys on (0001) GaN surfaces

“…The defects most commonly found during experimental growths of GaN and InGaN include stacking faults and associated mixed polytypism, [33][34][35][36][37][38] domain and grain boundaries, 36,39-41 threading 36,40,[42][43][44][45] and misfit dislocations, 12,[46][47][48][49][50] surface roughness, 43,[51][52][53][54][55][56][57][58] surface-pits (most notably, socalled "V-defects" 59,60 and concatenated V-defect trenches 61 ), and bulk voids. 44,51,62,63 These defects have typically appeared either when growth conditions are poorly optimized (as when these materials and growth processes were first explored) or when conditions are pushed yet farther from equilibrium (as in ongoing attempts to expand or tailor growth-process methods for improved materials). Our largescale MD-based simulations of GaN and InGaN-alloy growth are at an exploratory stage and, thus, necessarily proceed at extreme growth rates and temperatures.…”

Strain relaxation of thick (11–22) semipolar InGaN layer for long wavelength nitride-based device

“…2(a)) might be caused by in-plane diffusion anisotropy and residual strain. 20,[24][25][26] In addition, phase separation and indium content fluctuations in InGaN layers could increase owing to defects or surface roughness. [27][28][29] Therefore, a (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) semipolar InGaN layer grown on an ELO GaN template was analyzed to minimize the effect of surface roughness and defects.…”