arXiv subjects

Nirmal Anand

Publications and source records attributed to Nirmal Anand.

3 recordsLinked to original sources

arXiv2025

High-Performance Self-Powered Photoelectrochemical Detection Using Scalable InGaN/GaN Nanowire Arrays

Photoelectrochemical photodetectors (PEC-PDs) are promising owing to their simple, low-cost fabrication, self-powered operation, high photoresponse, and environmental sensitivity. In this work, we report for the first time the self-powered PEC photodetection characteristics of nanowire (NW) based green-emitting InGaN/GaN multiple quantum well (MQW) PEC-PDs, fabricated via a scalable top-down approach.The device exhibits strong UV sensitivity with a peak at 365 nm and an extended response into the visible region.Notably, a high photoresponsivity of 330 mA/W was achieved at a lower illumination intensity of 0.7 mW/cm2. Furthermore, the photodetector demonstrates fast, stable, and reproducible performance across varying biases and illumination conditions. These results suggest that InGaN/GaN MQW nanowire-based PEC photodetectors hold strong promise for scalable, efficient, and stable self-powered optoelectronic applications

physics.app-ph↗

arXiv2025

InGaN Nanopixel Arrays on Single Crystal GaN Substrate

Indium gallium nitride (InGaN) quantum well (QW) micro- and nanoscale light-emitting diodes (LEDs) are promising for next-generation ultrafast optical interconnects and augmented/virtual reality displays. However, scaling to nanoscale dimensions presents significant challenges, including enhanced nonradiative surface recombination, defect and/or dislocation-related emission degradation and nanoscale pixel contact formation. In this work, we demonstrate strain-engineered nanoscale blue LED pixels fabricated via top-down nanostructuring of an all-InGaN quantum well/barrier heterostructure grown by plasma-assisted molecular beam epitaxy (PAMBE) on significantly low dislocation-density single-crystal GaN substrates. Sidewall passivation using atomic layer deposition (ALD) of Al2O3 enables excellent diode behavior, including a high rectification ratio and extremely low reverse leakage. Monte Carlo analyses suggest almost 100% yield of completely dislocation-free active regions for 450 nm nanopixels. Electroluminescence measurements show bright blue emission with a peak external quantum efficiency (EQE) of 0.46%. Poisson Schrodinger simulations reveal partial strain relaxation in the QW, effectively mitigating the quantum confined Stark effect (QCSE). Additionally, finite-difference time-domain (FDTD) simulations confirm that the nanoscale geometry enhances light extraction efficiency by over 40% compared to planar designs, independent of substrate materials. These results establish a scalable pathway for dislocation free, high-brightness InGaN microLED arrays suitable for advanced display and photonic systems.

physics.app-ph↗

arXiv2025

On Apparent Absence of Green Gap in InGaN/GaN Quantum Disks and Wells Grown by Plasma-Assisted Molecular Beam Epitaxy

III-nitride based full-color blue, green and red-light emitting diodes are critically important for a broad range of important applications. To date, however, green or red color III-nitride light emitters grown by conventional growth techniques are limited in efficiency compared to blue emitters. As opposed to metal-organic chemical vapor deposition (MOCVD), while grown by plasma-assisted molecular beam epitaxy (PAMBE), the most intense emission is generally observed in the green spectral region in InGaN/GaN based light emitters. Such counterintuitive phenomenon of efficiency increase with increasing emission wavelength has been observed in both InGaN/GaN quantum-disks in nanowire and planar quantum-wells structures grown by PAMBE. Here, we experimentally show that the apparent absence of green gap in longer green wavelength is due to the difficulty of elimination of indium-rich non-radiative clusters and phase segregation in shorter blue wavelength quantum wells/disks.Excess indium due to the dissociation of the In-N bonds during growth lead to nitrogen vacancies and metallic inclusions. In radio-frequency PAMBE, the energy of the nitrogen radicals was found to be a driving force for indium incorporation.Our detailed growth and associated photoluminescence studies suggests that uniform phase and absence of metallic inclusion is the underlying mechanism of efficient green InGaN/GaN quantum wells/disks grown with sufficiently energetic plasma flux. Our study is valid for achieving very efficient green and red color InGaN/GaN and breaking the green gap bottleneck in quantum wells/disks grown by state-of-the-art high-power plasma-assisted molecular beam epitaxy

physics.app-ph↗