UV Emission from GaN Wires with m-Plane Core–Shell GaN/AlGaN Multiple Quantum Wells

Abstract

The present work reports high quality non-polar GaN/Al0.6Ga0.4N multiple quantum wells (MQWs) grown in core-shell geometry by metalorganic vapor phase epitaxy on the m-plane sidewalls of ̅ -oriented hexagonal GaN wires. Optical and structural studies reveal UV emission originating from the core-shell GaN/AlGaN MQWs. Tuning the mplane GaN QW thickness from 4.3 to 0.7 nm leads to a shift of the emission from 347 to 292 nm, consistent with Schrödinger-Poisson calculations. The evolution of the luminescence with temperature displays signs of strong localization, especially for samples with thinner GaN QWs and no evidence of quantum confinement Stark effect, as expected for non-polar m-plane surfaces. The internal quantum efficiency derived from the photoluminescence intensity ratio at low and room temperature is maximum (~7.3 %) for 2.6 nm-thick quantum wells, emitting at 325 nm and shows a large drop for thicker QWs. An extensive study of the PL quenching with temperature is presented.Two non-radiative recombination paths are activated at different temperatures. The low temperature path is found to be intrinsic to the heterostructure, whereas the process that dominates at high temperature depends on the QW thickness and is strongly enhanced for QWs larger than 2.6 nm, causing a drop of the internal quantum efficiency.

Toward Crack-Free Core–Shell GaN/AlGaN Quantum Wells

“…32,33 For both structures A and B, the first series of samples are studied by varying the QW thickness with the growth time. Based on TEM measurements previously performed on these structures, 18 the QW and barrier growth rates have been measured to be equal to V QW = 1.3 ± 0.5 nm•min −1 and V barrier = 4.3 ± 1.2 nm•min −1 , and the estimated thicknesses are therefore 5 nm for the barriers and from 2.6 to 0.2 nm for GaN QWs (for growth time varying from 120 to 10 s). Figure 3a shows some SEM images of the upper part of typical A-type core−shell GaN wires for several GaN QW growth times (120, 60, 20, 10 s).…”

“…16,17 In the case of GaN wires, a tunable emission down to 290 nm has been demonstrated with core/shell GaN/ AlGaN MQWs by decreasing the QW thickness. 18 Moreover, efficient carrier transport and electroluminescence in the UV-A,B range have been demonstrated with core−shell AlGaN/ GaN n−i−p structures and AlGaN/AlGaN QWs, respectively. 19,20 Although UV-C emission was demonstrated using core−shell AlGaN/AlN QWs on AlN wires, the issue of electrical injection into AlN wire impedes the development of electroluminescent (EL) devices.…”

Coherent-interface-induced strain in large lattice-mismatched materials: A new approach for modeling Raman shift

“…( 7) with R GaN = 6.5 ± 0.3 and R AlN = 7.7 ± 0.4 can be used to correctly estimate the biaxial strain in IIInitrides via Raman spectroscopy. The considerable application potential of the present findings could benefit a broad readership interested in III-nitride-based optoelectronics and power electronics devices [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][85][86][87][88]].…”

“…Research in wide-bandgap III-nitride semiconductors continues to progress rapidly, especially for the materials with bandgap exceeding that of gallium nitride (3.4 eV). Specifically, III-nitride based heterostructures provide new opportunities for a wide range of research and device applications, such as piezotronics and piezophototronics [1], self-powered photoelectrochemical-type photodetectors [2], room-temperature quantum emitters [3], single photon emitters [4][5][6], resonant tunneling diodes [7], highelectron-mobility transistors [8,9], efficient photoelectrocatalysts for solar water splitting [10], multi-wavelength light-emitting diodes (LEDs) [11,12], and deep ultraviolet (DUV)-LEDs [13][14][15][16][17]. AlGaN-based DUV-LEDs represent a sustainable alternative to replace the environmentally harmful conventional mercury lamps [18] and thus, are becoming crucial for many applications such as water purification and/or inactivation of microorganisms, including bacteria, fungi, and viruses [19,20].…”

Carrier dynamics near a crack in GaN microwires with AlGaN multiple quantum wells

“…9 A particularly promising approach is based on m-plane core-shell wires. [10][11][12][13][14][15] In this geometry, the absence of the quantum confined Stark effect and the increased emitting area contribute to the mitigation of the detrimental effects that appear at high carrier densities. Furthermore, core-shell wires have already been used to develop flexible LEDs, 16 this configuration could then lead to flexible UV LEDs.…”