InGaN/GaN Multiple Quantum Wells Grown on Nonpolar Facets of Vertical GaN Nanorod Arrays

Abstract

Uniform GaN nanorod arrays are grown vertically by selective area growth on (left angle bracket 0001 right angle bracket) substrates. The GaN nanorods present six nonpolar {1⁻100} facets, which serve as growth surfaces for InGaN-based light-emitting diode quantum well active regions. Compared to growth on the polar {0001} plane, the piezoelectric fields in the multiple quantum wells (MQWs) can be eliminated when they are grown on nonpolar planes. The capability of growing ordered GaN nanorod arrays with different rod densities is demonstrated. Light emission from InGaN/GaN MQWs grown on the nonpolar facets is investigated by photoluminescence. Local emission from MQWs grown on different regions of GaN nanorods is studied by cathodoluminescence (CL). The core-shell structure of MQWs grown on GaN nanorods is investigated by cross-sectional transmission electron microscopy in both axial and radial directions. The results show that the active MQWs are predominantly grown on nonpolar planes of GaN nanorods, consistent with the observations from CL. The results suggest that GaN nanorod arrays are suitable growth templates for efficient light-emitting diodes.

Ultra-High-Density Arrays of Defect-Free AlN Nanorods: A “Space-Filling” Approach

“…The type and density of the TDs were investigated by weak beam dark field TEM imaging. For detailed analysis of the dislocation movement within the crystal structure the sample was cut in the (10-10) and (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) zone axes. The samples were then tilted to a 2 beam condition in the g = (11-20) and g = (10-10) directions respectively, where only the edge and mixed (edge and screw) type dislocations were visible.…”

“…These newly exposed planes allow growth, of quantum wells that do not suffer from the severe band distortion caused, by piezoelectric fields that is an issue with c-plane polar (0001) orientated growth. 11,12 Nanorod arrays with high fill factors also lead to a much more efficient usage of substrate compared to planar growth. Close packed nanorods have the potential to counter act the wellknown issue of droop in III-Ns by reduced current densities in the junction at constant total currents.…”

Investigation of indium gallium nitride facet-dependent nonpolar growth rates and composition for core–shell light-emitting diodes

“…In this respect, core-shell [3][4][5] InGaN/GaN nanorods (NRs) are of considerable interest due to their large surface area of nonpolar planes or facets with lower number of defects, 6 the potential for high surface to volume ratio, 7 and QWs grown on their nonpolar sidewalls not being subject to the detrimental QCSE. These reasons provide a strong motivation for investigating their growth by the commercially preferred metalorganic vapor phase epitaxy (MOVPE) method.…”

“…15,18,19 In contrast to planar layer growth, uniform InGaN growth on NRs is difficult because the three-dimensional (3-D) growth mode leads to facet-dependent growth rates and indium nitride (InN) incorporation, leading to emission at multiple peak wavelengths. 4,5,17,20 Further, InGaN growth on pre-etched GaN NRs can be nonuniform for closely packed arrays, 12,21 indicating a likely dependence of indium mole fraction incorporation on NR height and spacing.…”

Site controlled red-yellow-green light emitting InGaN quantum discs on nano-tipped GaN rods

“…[11][12][13] These dislocation free GaN nanostructures are also reported to increase light extraction efficiency and enlarge the light emitting surface. [14][15][16] Additionally moving from bulk to nanoscale provides many new optical properties [17][18] bridging the green gap.…”