Vertically aligned GaN nanotowers (NTs) were grown on the Si (111) substrate by plasma-assisted molecular beam epitaxy to design a highly responsive ultraviolet (UV) photodetector. The UV detector fabricated on a bare GaN-NT array yielded highly sensitive and repeatable device characteristics attributed by high responsivity (R), low noise equivalent power (NEP), and a high external quantum efficiency (EQE) of 484.77 A/W, 1.76 × 10 −13 W.Hz -1/2 , and 1.85 × 10 5 %, respectively. Furthermore, the developed UV photodetector demonstrated fast response with excellent stability when functionalized with Au nanoparticles and ZnO nanorods. This hybridized GaN-NT-based device with ZnO nanorods and Au nanoparticles significantly accelerated the performance of the device where a prominent threeorder reduction under dark current is observed along with gigantic R, lower NEP, and an extremely enhanced EQE of 7042 A/W, 1.84 × 10 −14 W.Hz -1/2 , and 2.7 × 10 6 %, respectively. The mechanism elaborating the enhanced device performance with a localized surface plasmon effect has been discussed through an energy band diagram. The fabricated highly sensitive device can lead the path toward future optoelectronic applications of integrated III-nitride technology.

Gallium nitride (GaN) and aluminium gallium nitride (AlGaN) are promising materials for optoelectronics because of their direct band gap and high electron mobility. However, their optical absorbance being limited to within the ultraviolet (UV) range constrains their deployment in broadband photodetectors. Here, we combine three-dimensional (3D) epitaxial GaN and AlGaN thin films with visible-spectrum active two-dimensional (2D) molybdenum disulphide (MoS2) to create a 2D/3D hybrid that is active across a broadband spectrum. The interfacial properties of 2D/3D heterojunctions are thoroughly investigated on an industrially compatible silicon platform where a staggered gap (type II) band structure leads to a rectifying heterojunction phenomenon. It is shown that the optical absorbance spectra can be broadened by several hundreds of nanometers using this hybrid approach. As a result, these heterostructures are promising to cover broadband photodetection from ultraviolet (UV)-A (UV-B) to visible solar spectrum, thereby enhancing the practical utility of GaN and its alloys.

The fabrication of unique taper-ended GaN-Nanotowers structure based highly efficient ultraviolet photodetector is demonstrated. Hexagonally stacked, single crystalline GaN nanocolumnar structure (nanotowers) grown on AlN buffer layer exhibits higher photocurrent generation due to high quality nanotowers morphology and increased surface/volume ratio which significantly enhances its responsivity upon ultraviolet exposure leading to outstanding performance from the developed detection device. The fabricated detector display low dark current (~ 12 nA), high ILight/IDark ratio (> 104), fast time-correlated transient response (~ 433 µs) upon ultraviolet (325 nm) illumination. A high photoresponsivity of 2.47 A/W is achieved in self-powered mode of operation. The reason behind such high performance could be attributed to built-in electric field developed from a difference in Schottky barrier heights will be discussed in detail. While in photoconductive mode, the responsivity is observed to be 35.4 A/W @ − 3 V along with very high external quantum efficiency (~ 104%), lower noise equivalent power (~ 10–13 WHz−1/2) and excellent UV–Vis selectivity. Nanotower structure with lower strain and dislocations as well as reduced trap states cumulatively contributed to augmented performance from the device. The utilization of these GaN-Nanotower structures can potentially be useful towards the fabrication of energy-efficient ultraviolet photodetectors.

The nanoplasmonic impact of chemically synthesized Au nanoparticles (Au NPs) on the performance of GaN nanostructure-based ultraviolet (UV) photodetectors is analyzed. The devices with uniformly distributed Au NPs on GaN nanostructures (nanoislands and nanoflowers) prominently respond toward UV illumination (325 nm) in both self-powered as well as photoconductive modes of operation and have shown fast and stable time-correlated response with significant enhancement in the performance parameters. A comprehensive analysis of the device design, laser power, and bias-dependent responsivity and response time is presented. The fabricated Au NP/GaN nanoflower-based device yields the highest photoresponsivity of ∼ 380 mA/W, detectivity of ∼ 1010 jones, reduced noise equivalent power of ∼ 5.5 × 10–13 W Hz–1/2, quantum efficiency of ∼ 145%, and fast response/recovery time of ∼40 ms. The report illustrates the mechanism where light interacts with the chemically synthesized nanoparticles guided by the surface plasmon to effectively enhance the device performance. It is observed that the Au NP-stimulated local surface plasmon resonance effect and reduced channel resistance contribute to the augmented performance of the devices. Further, the decoration of low-dimensional Au NPs on GaN nanostructures acts as a detection enhancer with a fast recovery time and paves the way toward the realization of energy-efficient optoelectronic device applications.

An unprecedented excitation energy dependent dual emission from SrZnO2 nanophosphors is observed, predicting its applicability for switchable light emitting devices.

One of the dominant sources of energy production is burning fossil fuels (coal, natural gas, and petroleum), which emit different optical traces (ultraviolet to infrared). A self-driven broadband optical detector is essential for monitoring these optical signals in harsh environments because it is challenging to apply additional bias under high-temperature conditions. However, the existing optical detectors are constrained to operate at room temperature or require additional bias and present practical limitations in high-temperature operating environments. This study introduces a unique coco palm-like MoS 2 /GaN heterojunction-based self-powered photodetector that operates in the broadband spectral range from ultraviolet-C to near-infrared. The fabricated detector displays the highest responsivity of 379 mA W −1 under no applied bias at room temperature. The photodetector also exhibits consistent performance at high operating temperatures (up to 250 °C). Under self-driven conditions, the device possesses the highest responsivity of 360 mA W −1 at 250 °C. The heterostructure-based device also achieves the best responsivity of 2.8 × 10 6 mA W −1 at 8 V applied bias and has remarkable low-light detection abilities down to 9 femto-Watts. The hightemperature-operated self-driven broadband photodetector opens up possibilities for in situ monitoring of optical radiations from diverse industrial processes in challenging conditions and for optical signature-generating systems in the automobile, aerospace, and energy production industries.

We report, for the first time, the influence of oxygen vacancies on band structure and local electronic structure of $$\hbox {SrZnO}_2$$ SrZnO 2 (SZO) nanophosphors by combined first principle calculations based on density functional theory and full multiple scattering theory, correlated with experimental results obtained from X-ray absorption and photoluminescence spectroscopies. The band structure analysis from density functional theory revealed the formation of new energy states in the forbidden gap due to introduction of oxygen vacancies in the system, thereby causing disruption in intrinsic symmetry and altering bond lengths in SZO system. These defect states are anticipated as origin of observed photoluminescence in SZO nanophosphors. The experimental X-ray absorption near edge structure (XANES) at Zn and Sr K-edges were successfully imitated by simulated XANES obtained after removing oxygen atoms around Zn and Sr cores, which affirmed the presence and signature of oxygen vacancies on near edge structure.

In presented work, excitation selective novel cool and cold white emission is reported from dysprosium (Dy) doped SrZnO2 nanophosphors, synthesized by combustion technique. The host lattice provided selective excitation routes for Dy3+ levels and intrinsic defects levels via charge transfer (270 nm) and host defects absorption bands (375 nm), respectively. The emission due to Dy3+ levels was found to be exhibiting cool white emission and that from intrinsic defects was cold white emission, as characterized from correlated color temperature. UV irradiated glow curve analysis complemented the results by exhibiting signal due to Dy assisted traps on near UV exposure (254 nm) and that of host related traps at far UV exposure (365 nm). The luminescence phenomenon is comprehended through proposed band model. The obtained results proclaimed SrZnO2:Dy as a potential member among white emitting phosphors to be used as standard daylight sources in commercial and aesthetic lighting.