Metal Semiconductor Metal (MSM) photodetector devices based on metal organic chemical vapour deposition grown InGaN/GaN heterostructures with Ni/Au contacts has been fabricated with activity under near ultraviolet/visible region of spectra. Composition controlled InGaN/GaN heterostructures has been utilized for device fabrication to realize its correlation with the electrical performance and responsivity of the device. The steady and transient performance of the as designed photodetectors were investigated and a photo response time <9 ms, responsivity of 0.920 A/W and high detectivity range of similar to 3.46 x 10(13) Jones has been achieved at a wavelength of 360 nm for an indium composition of 10%. We have observed that an increasing indium content in InGaN layers up to an optimum value resulted in an increase in device performance which has been explained with the help of various structural, morphological, optical and spectroscopic analysis. The obtained results were competing with the many previously reported photodetectors.

Device fabrication using semiconductor nanostructures for detecting ultraviolet (UV) radiations, especially UV-A (320-400 nm) has received much attention both at laboratory level and in commercial endeavours. In this work, we have attempted catalytic growth of good quality gallium nitride nanowires (GaN NWs) for utilization in building high-responsive optoelectronic devices. In order to obtain good quality control in the growth of GaN NWs, single metal catalyst has been replaced with a binary catalytic alloy of gold-palladium (Au-Pd). Scanning electron microscopy (SEM) results revealed that the NWs grown are long, dense and uniformly thick in size. The hexagonal crystal structure of the grown NWs was confirmed using x-ray diffractometer (XRD) and transmission electron microscopy (TEM). Other characterization results like x-ray photoelectron spectroscopy (XPS), Raman spectroscopy and photoluminescence (PL) spectroscopy were helpful in determining the compositional and optical properties of the samples. The fabricated GaN NWs based UV-A photodetector showcased a fast rise time (tau(r)) and fall time (tau(f)) of around 22 and 29 ms, an ultrahigh responsivity (R) and sensitivity (S) of about of 11.87 x 10(7) A/W and 3.8 x 10(4)%, an external quantum efficiency (EQE) of 9.45 x 10(9)%, very high detectivity (D) of 3.83 x 10(18) Jones and high wavelength selectivity in the UV-A regime. (C) 2021 Elsevier B.V. All rights reserved.

Well-defined Dahlia type gallium nitride flowers (GaNFs) have been synthesized on c-plane sapphire substrates at different growth conditions using chemical vapour deposition system. The growth was carried out without any catalyst medium for favouring the nucleation process. Crystal structure of the GaNFs was obtained using x-ray diffractometer (XRD). Scanning electron microscopy (SEM) revealed the morphology of GaNFs. The elemental traces and compositions of the samples were obtained using energy dispersive x-ray (EDX) spectroscopy and x-ray photoelectron spectroscopy (XPS). The optical properties of the samples were analysed using cathodoluminescence (CL) spectroscopy and Raman spectroscopy. From the current-voltage (I-V) response, it was observed that there are no interface and surface related inhomogeneities in the samples. The fabricated photodetector showcased good device performance due to high carrier density in the sample.

Currently several type of energy sources exist in the modern world. The energy makes people's life more comfortable, easy, time savings, fast transformation of information and various modes of transmission. Because of large demand of energy, efforts on production of energy increases day by day which subsequently increase serious environmental concerns such as pollution and lack of existing natural resources. In this respect, several attempts have been proposed for new type of renewable and chemical energy systems to overcome the economic burden, global warming and environmental problems caused by the use of conventional fossil fuels. Hydrogen production via water splitting is a promising and ideal route for renewable energy using the most abundant resources of solar light and water. Cost effective photocatalyst for Photoelectrochemical (PEC) water splitting using semiconductor materials as light absorbers have been extensively studied due to their stability and simplicity. Over the past few decades, various metal oxide photocatalysts for water splitting have been developed and their photocatalytic application was studied under UV irradiation. Alternative semiconductor photocatalyst should harness solar energy in the visible light, one such semiconductor material is indium gallium nitride (InGaN), owing to its suitable and tunable energy band-gap, chemical resistance and notable photoelectrocatalytic activity. This review article is initiated with the brief introduction about the origin and methods of production of hydrogen gas from both renewable and nonrenewable energy sources. Multi-functional properties and applications of InGaN are described along with past and recent efforts of InGaN materials for hydrogen evolution by several investigators are provided in detail. In addition, future prospects and ways to improve the PEC performance of InGaN are presented at the end of this review.

Gallium nitride (GaN) was epitaxially grown on nitrogen doped single layer graphene (N-SLG) substrates using chemical vapour deposition (CVD) technique. The results obtained using x-ray diffractometer (XRD) revealed the hexagonal crystal structure of GaN. Photoluminescence (PL) spectroscopy, energy dispersive x-ray (EDX) spectroscopy and x-ray photoelectron (XPS) spectroscopy revealed traces of oxygen, carbon and nitrogen occurring either as contamination or as an effect of doping during the GaN growth process. In addition, PL revealed a weak yellow luminescence peak in all the samples due to the presence of N-SLG. From the obtained results it was evident that, presence of N-SLG underneath GaN helped in improving the material properties. It was seen from the current–voltage (I–V) response that the barrier height estimated is in good agreement with the Schottky–Mott model, while the ideality factor is close to unity, emphasizing that there are no surface and interface related inhomogeneity in the samples. The photodetector fabricated with this material exhibit high device performances in terms of carrier mobility, sensitivity, responsivity and detectivity. The hall measurement values clearly portray that, the GaN thus grown possess high electron contents which was beneficial in attaining extraordinary device performance.

Growth of gallium nitride nanowires on etched sapphire and GaN substrates using binary catalytic alloy were investigated by manipulating the growth time and precursor-to-substrate distance. The variations in behavior at different growth conditions were observed using X-ray diffractometer, Raman spectroscopy, X-ray photoelectron spectroscopy, cathodoluminescence spectroscopy, optical microscopy, atomic force microscopy, and scanning electron microscopy. It was noticed that, in respect of both the substrates, when growth time and/or precursor-to-substrate distance is increased, thickness of the nanowires around the etch pits remains unaltered, but there is variation in the density of nanowires. In addition, formation of gallium nitride microwires within the etch pits was also observed on etched sapphire substrates. Similarly, the thickness and density of the microwires were found to increase with increase in growth time and decrease with increase in precursor-to-substrate distance. The dimensionality scaling of gallium nitride was found to have a positive effect in improving the luminescence property and band gap of the grown nanowires. This method of nanowire growth can be helpful in increasing the probability of multiple reflections in the materials which makes them a suitable candidate for optoelectronic devices.

The growth behaviour of gallium nitride nanowires grown on nickel/sapphire template has been investigated. The nanowires were grown using chemical vapour deposition method by vapour-liquid-solid process. The growth was carried out by maintaining the growth temperature and carrier gas flow rate as constants, while the time of growth was altered between 0.5 and 1.5 h. The peaks obtained using X-ray diffractometer confirmed the crystalline nature of the samples. The scanning electron microscopy results revealed the stage by stage growth morphologies of the samples. Average diameter of the nanowires was found to be ~300 nm with lengths up to a few micrometers. Based on the characteristic spectra obtained from UV-Vis spectrometer, bandgap of the nanowires was estimated to be 3.3 eV.

The structural, optical, morphological and electrical properties of the low energy N ion implanted InGaN/GaN heterostructures have been investigated. These heterostructures were grown by metal-organic chemical vapor deposition. The compositional fluctuations and crystalline quality of pristine and implanted samples are measured by the high-resolution x-ray diffraction. The tricking asymmetric (1 0   −1 5) GaN and InGaN peaks of ω  −  2θ and omega diffraction patterns are then resolved using reciprocal space mapping. The morphology of N ion implanted InGaN sample shows a decrease in density of the V-pits and hillocks with increasing N ion fluences. The atomic percentage of In, Ga and N are estimated using x-ray photoelectron spectroscopy. The Raman studies showed the E2 high and A1 (LO) modes of GaN and InGaN for pristine and implanted samples which also confirm that the linear dependence of In composition with the N ion implantation fluences. The photoluminence results confirm the suppression of yellow luminescence peak after implantation. The Hall measurements confirm the enhancement in electron mobility after implantation which inevitably suppressed the carrier concentration with decreased nitrogen vacancies. The low energy N ion implantation increases In composition and reduction of In clusters in the InGaN layer which have a technological significance in InGaN based optoelectronic applications.

The InGaN/GaN based Quantum Well structures were grown on c-plane sapphire substrate using metal-organic chemical vapor deposition. Crystalline quality has been investigated using High-resolution X-ray diffraction (HRXRD) analysis and total dislocation densities of screw and edge types in the GaN epilayer have been calculated. The thickness and indium composition of the InGaN was determined by HRXRD. From simulation fit, the composition of indium was found to be 12 and 15

In this work, lattice-matched AlInGaN/GaN epilayers are grown on c-plane Al2O3 substrate by metal organic chemical vapor deposition technique. The structural and optical properties of AlInGaN/GaN epilayers have been studied and compared. TMIn and TMAl flow is believed to have a direct impact on the quality of AlInGaN epilayer. By varying In and Al composition in AlInGaN epilayer, dislocations (V-pit density) have been found to decrease, indicating lower threading dislocation density as confirmed by HRXRD and AFM. Reciprocal space mapping analysis has confirmed that the growth of AlInGaN on GaN buffer is a fully lattice matched growth. AlInGaN exhibits two emissions originating from In(Ga)N clusters and the AlInGaN random matrix is confirmed by photoluminescence. In the Raman spectra of AlInGaN, A(1) (LO) mode at 751 cm(-1) and In(Ga)N clustering A(1)(LO) mode at 680 cm(-1) is observed. These findings open the new advancement in the field of opto-electronic applications.

Gallium nitride (GaN) nanowires (NWs) are one of the most promising candidates for photoelectrode materials due to their tunable band edge potentials and high stability in electrolytes. In this study, GaN NWs were grown on sapphire (Al2O3) (002) and silicon (Si) (111) substrate by chemical vapor deposition (CVD) method. High quality of GaN NWs on sapphire and silicon were confirmed by powder X-ray diffraction (XRD). Structural characterization of the synthesized NWs were performed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The images revel the pristine and smooth surface of GaN NWs. Further, optical properties of GaN NWs were investigated at room temperature photoluminescence emission. The photocurrent density of GaN/Si NWs is found to be higher than that of GaN/Al2O3 NWs. The GaN/Si NWs having large surface area, are grown in a much simpler method. GaN/Si NWs are potential candidate for hydrogen energy generation, due to their enhanced water splitting efficiency by utilizing solar energy. (C) 2018 Elsevier B. V. All rights reserved.

This paper reports on the unique approach adopted for the growth of vertically aligned two-dimensional AlN microwall arrays by a catalyst-free metal organic chemical vapor deposition (MOCVD) system via a two-step growth method. Wall-like structures are formed on the surface modified GaN/Al2O3 template using simple H3PO4 wet chemical etching, leading to growth of AlN microwall arrays. Large area and vertically aligned AlN microwalls with c-orientation could be grown on GaN/Al2O3 template, at the growth temperature and flow rate of 900 degrees C and 30 sccm respectively. The dimensions of AlN microwalls are 700 nm to 1.5 mu m in diameter and up to 400 nm-500 nm in height. The structural, morphological and optical characterization of these samples have been carried out by HRXRD, SEM, XPS, Raman and Photoluminescence. AlN microwall arrays are wurtzite crystal structure with a small full width at half-maximum (352 arcsec) of (0002) X-ray rocking curve confirmed by High resolution X-ray diffraction. PL spectrum confirms defect related levels which enhances the visible emission. The experimental results have confirmed the two-dimensional AlN microwalls with high crystallinity and remarkable optical properties.

Employing three different active layer widths, aluminium gallium nitride-based double heterostructures have been grown on GaN template by metal-organic chemical vapour deposition. The crystalline quality of the heterostructures has been investigated using high-resolution X-ray diffraction analysis. Optical and decay time studies have been carried out using room-temperature photoluminescence and time-resolved photoluminescence, respectively. The interface recombination velocity (S) between active and barrier layers has been determined.

Irradiation effects of 120 MeV silicon ion with the fluence of 5 x 10(12) ions/cm(2) at room temperature and low temperature (77 K) on AlGaN/GaN heterostructures have been studied to probe the radiation tolerance for space applications. XRD results explicitly showed there were no compositional changes and additional phase formation due to irradiation. Smooth surface with atomic steps and terrace features has been observed in the pristine sample; upon irradiation, the surface become rough with annihilated surface steps. Atomic force microscopy images depict the nano and micro structures formation for the silicon ion irradiated AlGaN/GaN samples at room temperature and low temperature (77 K), respectively. Photoluminescence measurements revealed the blue shift of AlGaN layer in the low temperature irradiated samples. Intensity of defect peaks around 2.5-3.2 eV increases for irradiated samples. Low temperature irradiation decreases the radiation tolerance and increases the defects and surface roughness of the AlGaN/GaN heterostructures.

In the present study of AlGaN/GaN heterostructures with high quality AlN interlayer (AlN-IL) were grown by metal organic chemical vapor deposition (MOCVD) on c-plane sapphire substrate. The AlN inter-layer thickness was varied as 1, 2 and 3 nm. The High-resolution X-ray diffraction (HRXRD) FWHM for (002) plane of GaN was measured for AlGaN/GaN with different AlN-IL thickness. The surface roughness was measured using Atomic Force Microscope (AFM). The Photoluminescence (PL) band edge emission, the room temperature and low temperature hall measurement show the enhancement of two-dimensional electron gas (2DEGs) sheet carrier density due to AlN-IL. The results have been discussed in detail.

AlxInyGa1-x-yN epilayers have been grown by metal organic chemical vapor deposition (MOCVD) at different temperatures from 740 to 940 °C. The incorporation of indium increases with decreasing growth temperature, while the incorporation of Al composition was 30–40 %. The optical properties of the samples have been investigated by photoluminescence (PL). The results show that the sample grown at 890 °C exhibits the best crystalline and optical quality.

Aluminum gallium nitride-based double heterostructures with two different active layer widths have been grown on GaN templates by metalorganic chemical vapor deposition. Crystalline quality has been investigated using high-resolution x-ray diffraction analysis, and screw, edge, as well as total dislocation densities in the GaN epilayer have been calculated. The dislocation density of GaN has been found to be on the order of 108 cm−2. The nominal Al composition and in-plane strain ε xx for the AlGaN layer grown on the GaN layer have been measured by asymmetric reciprocal-space mapping. Surface properties and cross-sectional views of the samples have been analyzed using atomic force microscopy (AFM) and field-emission scanning electron microscopy (FESEM), respectively. Room-temperature time-resolved photoluminescence and photoluminescence measurements have been performed on Al0.18Ga0.82N/Al0.45Ga0.55N double heterostructures and the GaN template. The interface recombination velocity (S) of AlGaN-based double heterostructures has been calculated using carrier decay time measurement, increasing from 8.7 × 103 cm/s to 13.4 × 103 cm/s with varying active layer thickness.

AlGaN is a promising material to develop UVLEDs and HEMT devices due to the direct wide-band gap material. In the present investigation, AlxGa(1)-xN alloys were grown on c-plane sapphire substrate by MOCVD. Al content x was varied in the composition range 0 <= x <= 0.6. The thickness and Al composition of the AlGaN was determined by HRXRD. The growth rate decreases on increasing the composition of Al. The critical thickness of pseudomorphic AlGaN layer decreases on increasing the composition. Thick layers resulted in cracks and it is important to grow thick layers with high aluminum content free from crack for deep UV LEDs.

Zn3P2 epilayers were grown on InP (100) substrates by liquid phase epitaxy (LPE) using In solvent. Zinc composition in the epilayers was varied by changing the zinc mole fraction in the growth melt and was confirmed by energy dispersive X-ray analysis (EDAX). Stoichiometric Zn3P2 epilayers were subjected to 100 MeV Ni ion irradiation with various ion fluences of 1 x 10(10) to 1 x 10(13) ions/cm(2) at 77 K. From the high resolution X-ray diffraction (HRXRD) of 100 MeV Ni ion irradiated epilayers, the decrease in the peak intensities and increase in the FWHM values were observed. AFM analysis revealed the formation of nanotracks in the irradiated Zn3P2 epilayers. Hall measurements showed the decrease in carrier mobility with the increase of ion fluence. The absorption band edge of Zn3P2 gradually decreased from 1.49 eV to 1.42 eV upon increasing the ion fluence. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Group III-V nitrides have become versatile semiconducting materials for short wavelength LEDs, high temperature transistors. The growth and device processing of these materials are significant due to unusually high bond energies of nitrides. Inspite of high dislocations densities in the order of 10(9)cm(-2) the optical and electronic devices based on nitrides show high performance compared to conventional semiconductor devices. Understanding of the behavior of dislocations in these materials structures are very important for the fabrication of devices. In the present study, GaN was grown on sapphire substrates using MOCVD. The dislocation density of GaN has been estimated by wet etching and HRXRD. The results have been correlated with the growth conditions. The dislocation density of the samples was found to be between 3.5x10(9)cm(-2) and 5.0x10(8)cm(-2).