Browsing by Author "Jayasakthi, M."
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- Effects of indium flow rate on the structural, morphological, optical and electrical properties of InGaN layers grown by metal organic chemical vapour deposition
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2019-11-30) Prabakaran, K.; Raju, Ramesh; Arivazhagan, P.; Jayasakthi, M.; Sanjay, S.; Surender, S.; Pradeep, S.; Balaji, M.; Baskar, K.InGaN/GaN heterostructures were grown on c-plane sapphire substrates using metal organic chemical vapour deposition by varying the trimethylindium flow rate as 7, 10 and 14 μmol/min. The structural, morphological, optical and electrical properties of InGaN layers were investigated. Crystalline quality, dislocation densities comprising of screw and edge types in InGaN and GaN layer have been analyzed using High-Resolution X-ray Diffractometer (HRXRD). The composition of Indium (In) in the InGaN layers was estimated around 8–10% which was found to be dependent on the In flow rate. The strain between InGaN and underlying GaN layer have been analyzed through reciprocal space mapping studies along the (1 0–1 5) plane in InGaN/GaN heterostructures. The features of V and trench defects were observed using scanning electron microscopy and atomic force microscopy respectively. The V and trench defect density has been correlated with the pre-existing threading dislocation density estimated using HRXRD measurements. Also the trench defects were observed to be a coalescence of V defects in InGaN layers. The photoluminescence results showcased the band edge emission peaks at three different points (primary flat, centre, and Edge). These peak variations were found to be red shifted in all three points. This may be due to the fluctuations in the Indium composition and its corresponding V and trench defects respectively. The Hall measurements exhibit an alteration in the semiconducting behavior with respect to V and trench defect surrounded InGaN layers. And, it also emphasizes that the compressive strain in underlying GaN can lead to the high sheet concentration compared to the tensile strain in the underlying GaN layer. It clearly suggests that the V and trench defect surrounded InGaN layers are the suitable material for next generation optoelectronics applications. - Influence of InGaN interlayer thickness on GaN layers grown by metal organic chemical vapour deposition
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2019-03-01) Prabakaran, K.; Jayasakthi, M.; Surender, S.; Pradeep, S.; Sanjay, S.; Ramesh, Raju; Balaji, M.; Baskar, K.InGaN interlayer was grown between GaN layers on sapphire substrate using metal organic chemical vapour deposition. The crystalline quality of the sample was investigated using high-resolution X-ray diffraction. The indium composition and InGaN thickness were determined to be 10–15% and 5–10 nm, respectively. Transmission electron microscopy image revealed the interfacial characteristics of the InGaN and GaN layers. Raman spectroscopy revealed prominent GaN peak positions with InGaN shoulder peaks. The growth mode of InGaN and GaN was determined as nanoislands with helical-like morphology by atomic force microscopy. Hall measurement showcased improvement in the mobility and bulk concentration for the GaN/InGaN (5 nm)/GaN structures. - Investigations on morphology, growth mode and indium incorporation in MOCVD grown InGaN/n-GaN heterostructures
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2018-12-01) Prabakaran, K.; Jayasakthi, M.; Surender, S.; Pradeep, S.; Sanjay, S.; Ramesh, R.; Balaji, M.; Baskar, K.InGaN layers were grown on n-GaN/GaN/sapphire template using metal organic chemical vapor deposition system by varying Indium (In) flow rate as 11, 13 and 14 μmol/min. The nanoisland growth mode was observed by atomic force microscopy. The thickness and composition of In in the InGaN layers were determined by high resolution X-ray diffraction technique. The composition of In was found to be 15–17% depending on the In flow rate. Photoluminescence from the InGaN layers exhibit multiple peaks ranging between 479 to 657 nm, originating from the distribution of In-rich InGaN nanoislands of various sizes giving rise to localized excitons due to the In composition fluctuations. It is interesting to note that, peak emissions at 539 nm, 549 nm and 543 nm showed red and blue shift with varying In flow rate of InGaN nanoisland structures which can be attributed to the quantum confined stark effect and quantum confinement effect. Hall Effect measurement clearly indicate the variations in the semiconducting behavior of the InGaN nanoislands which influenced the composition fluctuation. - Structural, morphological, optical and electrical characterization of InGaN/GaN MQW structures for optoelectronic applications
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2019-05-15) Prabakaran, K.; Jayasakthi, M.; Surender, S.; Pradeep, S.; Sanjay, S.; Ramesh, Raju; Balaji, M.; Gautier, Nicolas; Baskar, K.InGaN/GaN multiple quantum well (MQW) structures were grown on c-plane sapphire substrate using metal organic chemical vapour deposition technique by varying the MQW periods. The indium composition and thickness were estimated using high-resolution X-ray diffraction. InGaN well, GaN barriers and Indium composition were estimated as 3 nm, 18 nm and 16–18% using epitaxy smooth fit software. Reciprocal space mapping revealed that InGaN/GaN MQW samples were coherently strained. High-resolution transmission electron microscopy images confirmed good interface between the InGaN/GaN MQW structures. Atomic force microscopy and scanning electron microscopy exhibit decrease in the surface roughness with increase in the number of InGaN/GaN MQW periods with respect to the number of defects comprising of threading dislocations and hexagonal V-pits. Self-organized In(Ga)N like nanostructures with spiral growth mechanism was also observed due to the low temperature growth of p-GaN layer. The photoluminescence spectra of the MQWs showed a red-shift when the number of QW periods was increased due to quantum confined stark effect. Hall Effect measurement displayed good semiconducting behavior in the InGaN/GaN MQW structures. The carrier concentration values also emphasized adequate variations when number of periods was increased.