Unintentional indium incorporation into barriers of InGaN/GaN multiple quantum wells studied by photoreflectance and photoluminescence excitation spectroscopy

Abstract

InxGa1–xN/GaN single and multi quantum well (MQW) structures with x ≈ 0.13 were investigated optically by photoreflectance, photoluminescence excitation spectroscopy, and luminescence. Clear evidence of unintentional indium incorporation into the nominal GaN barrier layers is found. The unintentional In content is found to be around 3%. Inhomogeneous distribution of In atoms occurs within the distinct quantum well (QW) layers, which is commonly described as statistical alloy fluctuation and leads to the characteristic S-shape temperature shift of emission energy. Furthermore, differences in emission energy between the first and the other QWs of a MQW stack are found experimentally. This effect is discussed with the help of model calculations and is assigned to differences in the confining potential due to unwanted indium incorporation for the upper QWs.

Исследование распределения встроенных электрических полей в светодиодных гетероструктурах c множественными квантовыми ямами GaN/InGaN методом электроотражения

“…В результате КЯ, расположенные близко к n-GaN или p-GaN, играют роль буферных слоев, уменьшающих механические напряжения в центральной КЯ. [30] может быть связано с размытием границ барьер-яма изза диффузии индия в барьер GaN в процессе роста [31]. Расчет энергетических уровней показывает, что наиболее близкие переходы по энергии (3.12 ± 0.17) эВ (рис.…”

“…Другое объяснение происхождения этой линии может быть связано с диффузией In в барьерные слои [31]. Энергия перехода таких слоев становится меньше, чем энергия перехода в легированных слоях GaN, несмежных с КЯ InGaN.…”

Inhomogeneous broadening of optical transitions observed in photoluminescence and modulated reflectance of polar and non-polar InGaN quantum wells

“…Up to now ER spectroscopy was applied a few times to study InGaN QWs [20][21][22][23][24][25] but the problem of superposition of QW transitions related to different states present in ER spectra and the broadening of QW transitions associated with QW inhomogeneities was not carefully addressed. In general, such an issue is problematic to study experimentally since it is difficult to control independently QW fluctuations, i.e., to have a set of samples with fluctuating QW width without QW content fluctuations, and conversely to have a set of QWs with fluctuating QW content and without QW width fluctuations.…”

Influence of Quantum well Thickness Fluctuation on Optical Properties of InGaN/GaN Multi Quantum well Structure Grown by PA-MBE

“…[9] While it is possible to achieve long wavelength (λ> 530 nm) by simply increasing the indium content in the QWs, a number of problems related to the InGaN ternary alloy system become serious. When the InGaN film was grown over the critical thickness, a rough surface morphology is formed due to the lattice mismatch between InGaN and GaN [10].…”