Composition Fluctuation of In and Well-Width Fluctuation in InGaN/GaN Multiple Quantum Wells in Light-Emitting Diode Devices

Abstract

Abstract:In this paper, we have observed an atomic-scale structure and compositional variation at the interface of the InGaN/GaN multi-quantum wells~MQW! by both scanning transmission electron microscopy~STEM! using high-angle annular dark-field mode and atom probe tomography~APT!. The iso-concentration analysis of APT results revealed that the roughness of InGaN/GaN interface increased as the MQW layers were filled up, and that the upper interface of MQW~GaN/InGaN to the p-GaN side! was much rougher than that of the lower interface~InGaN/GaN tot he n-GaN side!. On the basis of experimental results, it is suggested that the formation of interface roughness can affect the quantum efficiency of InGaN-based light-emitting diodes.

Emission wavelength red-shift by using “semi-bulk” InGaN buffer layer in InGaN/InGaN multiple-quantum-well

“…Similar MQW thickness variation has been reported for a MQW with superlattice prelayer in G.H. Gu et al [22] and A. Even et al [10] Our MQW on SB has presumably more interface roughness in the last QW and this is attributed to the accumulated strain in the growth direction, [22] which is more prominent due to the more InGaN/GaN interfaces in the SB sample B.…”

“…Gu et al [22] and A. Even et al [10] Our MQW on SB has presumably more interface roughness in the last QW and this is attributed to the accumulated strain in the growth direction, [22] which is more prominent due to the more InGaN/GaN interfaces in the SB sample B. This interface roughness decreases the non-radiative recombination due to the tendency of scattering in the roughness.…”

Practical Issues for Atom Probe Tomography Analysis of III-Nitride Semiconductor Materials

“…In the case of III-nitrides, Galtrey et al in 2007 pioneered the application of APT to assess whether indium "clusters" were present in c-plane InGaN/ GaN multiple quantum wells (MQWs) (Galtrey et al, 2007). Thereafter, a number of studies have reported both polar (Galtrey et al, 2008;Bennett et al, 2011;Müller et al, 2012;Gu et al, 2013), semi-polar (Prosa et al, 2011) and non-polar (Riley et al, 2014;Tang et al, 2015) InGaN-based structures and AlN-containing materials (Choi et al, 2012;Mazumder et al, 2013). All of these studies rely on pulsed-laser APT.…”

“…Although it is generally known in the APT community that damage to the material can be limited by lowering the FIB accelerating voltage during the final "clean-up" step of, for instance, typical Cu/Co layers and Si materials (Larson et al, 1999;Thompson et al, 2006;Thompson et al, 2007), there is no clear consensus as to the optimal FIB conditions that should be employed for studying III-nitride materials in the ever increasing literature on these materials (Galtrey et al, 2007(Galtrey et al, , 2008Bennett et al, 2011;Prosa et al, 2011;Choi et al, 2012;Müller et al, 2012;Dawahre et al, 2013;Gu et al, 2013). Amidst these, variable "clean-up" FIB voltages, up to 5 kV, have been reported (Bennett et al, 2011;Gu et al, 2013). When investigating Gacontaining materials, this issue becomes challenging due to the question of differentiation of FIB-implanted Ga damage from Ga originally present in the sample.…”

A Brief Comment on Atom Probe Tomography Applications

“…The stoichiometry deficiency observed in APT analyses of nitrides and oxide at high laser pulse energy is well known (Devaraj et al, 2013;Kinno et al, 2014;Santhangopalan et al, 2015). For example, in the case of GaN, at the lowest laser energies, the apparent composition is nitrogen-rich, while higher laser energies results in gallium-rich (i.e., nitrogen-deficient) (Gu et al, 2013;Riley et al, 2014;Sanford et al, 2014). The origin of this trend is controversial until now, but one widely proposed interpretation is the formation of a significant amount of neutral N 2 gas molecules at low electric field (high laser energy) (Diercks et al, 2013;Gault et al, 2016).…”