Luminescence studies on green emitting InGaN/GaN MQWs implanted with nitrogen (original) (raw)
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Thin Solid Films, 2006
InGaN/GaN multiple quantum well light emitting diode structures have been grown on sapphire substrates by metalorganic chemical vapor deposition. They are investigated, in this study, by high-resolution X-ray diffraction, high-resolution transmission electron microscopy, photoluminescence, and photoluminescence excitation. HR-XRD showed multiple satellite peaks up to 10th order due to the quantum well superlattice confinement effects. These indicate the high quality of layer interface structures of this sample. Excitation power-dependent photoluminescence shows that both piezoelectric field-induced quantum-confined Stark effect and band filling effect influence the luminescent properties of this sample. Temperature-dependent photoluminescence of this sample has also been studied. The peak position of the PL exhibits a monotonic red-shift and the full width at half maximum of the PL band shows a W-shaped temperature-dependent behavior with increasing temperature. From the photoluminescence excitation results, a large energy difference, so-called Stokes shift, between the band-edge absorption and emission was observed.
Nano-structures and luminescence mechanisms of InGaN/GaN multiple quantum well light emitting diodes
The International Conference on Electrical Engineering, 2008
A series of InGaN/GaN MQW LEDs were prepared by low pressure metalorganic chemical vapor deposition (MOCVD) and studied on the nano-structural features correlated with optical properties, and luminescence emission mechanisms by analytical techniques of photoluminescence (PL), PL excitation (PLE), time resolved PL (TRPL), high-resolution (HR) X-ray diffraction (XRD) and HR transmission electron microscopy (TEM). They have shown the excellent optical and structural properties, evidenced by HRXRD, HRTEM and optical measurements. The quantum dot like structure features, unique T-behaviors of PL spectra, quantum confined Stokes effect, TRPL exploration with the variation of detecting energy and temperature and modeling analyses are studied and discussed.
Journal of Microscopy, 2017
In this work, we analyse the microstructure and local chemical composition of green-emitting In x Ga 1-x N/GaN quantum well (QW) heterostructures in correlation with their emission properties. Two samples of high structural quality grown by metalorganic vapour phase epitaxy (MOVPE) with a nominal composition of x = 0.15 and 0.18 indium are discussed. The local indium composition is quantitatively evaluated by comparing scanning transmission electron microscopy (STEM) images to simulations and the local indium concentration is extracted from intensity measurements. The calculations point out that the measured indium fluctuations may be correlated to the large width and intensity decrease of the PL emission peak.
Journal of Crystal Growth, 2011
InGaN/GaN quantum wells (QWs) with symmetrical ultra thin (about 0.5nm) low temperature GaN (LT-GaN) layers bounding each InGaN layer were grown by metal-organic vapor phase epitaxy (MOVPE). From the high resolution X-ray diffraction (HR-XRD) measurement, it showed improved well-barrier interface abruptness compared to the reference MQWs without the LT-GaN layers. In addition, the V-defect density and surface roughness were reduced, especially with the depth of V-defect as low as 0.7nm. Based on the temperature dependence photoluminescence (TDPL) experiments, the internal quantum efficiency (IQE) was increased from 21.2% to 30.1% by inserting the LT-GaN layers. The carrier lifetime obtained from room temperature time resolved photoluminescence (TRPL) measurement was 7.95ns, which was longer than 5.34ns for reference MQWs. These results indicated that these additional symmetrical thin LT-GaN layers enhanced the mobility of indium and gallium atoms as well as suppressed the indium desorption for growth high quality InGaN layers and in turn improved its structural and luminescence properties.
Carrier localization in In-rich InGaN/GaN multiple quantum wells for green light-emitting diodes
Scientific reports, 2015
Carrier localization phenomena in indium-rich InGaN/GaN multiple quantum wells (MQWs) grown on sapphire and GaN substrates were investigated. Temperature-dependent photoluminescence (PL) spectroscopy, ultraviolet near-field scanning optical microscopy (NSOM), and confocal time-resolved PL (TRPL) spectroscopy were employed to verify the correlation between carrier localization and crystal quality. From the spatially resolved PL measurements, we observed that the distribution and shape of luminescent clusters, which were known as an outcome of the carrier localization, are strongly affected by the crystalline quality. Spectroscopic analysis of the NSOM signal shows that carrier localization of MQWs with low crystalline quality is different from that of MQWs with high crystalline quality. This interrelation between carrier localization and crystal quality is well supported by confocal TRPL results.
Investigation of electron energy states in InGaN/GaN multiple quantum wells
Physica B: Condensed Matter, 2012
Blue light emitting diodes (LED) consisting of InGaN/GaN multiple quantum wells (MQWs) have been grown by metal organic chemical vapor deposition (MOCVD) on sapphire. The width of the quantum wells (InGaN) was maintained in the range of 3-5 nm with a barrier of 10-15 nm of GaN. Various diagnostic techniques were employed for the characterization of the InGaN/GaN heterostructure. Carrier concentration depth profile from C-V measurements demonstrated the presence of MQWs. The higher value of built-in voltage (15 V) determined from C À 2 -V plot also supported the presence of MQWs as assumed to alter the space-charge region width and hence the intercept voltage. Arrhenius plots due to DLTS spectra from the device revealed at least four energy states (eV) 0.1, 0.12, 0.15 and 0.17, respectively in the quantum wells, with respect to the barrier. Further the photoluminescence spectrum showed an InGaN-based broad band centered at 2.9 eV and the GaN peak at 3.4 eV. A comparison of the PL spectrum with the literature helped to estimate the indium content in the QW (InGaN) and its width to be $ 13% and $ 3 nm, respectively. The results were consistent with the DLTS findings.