arXiv subjects

Grzegorz Muziol

Publications and source records attributed to Grzegorz Muziol.

5 recordsLinked to original sources

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↗

arXiv2022

Impact of interfaces on photoluminescence efficiency of high indium content InGaN quantum wells

InGaN-based light emitting diodes (LEDs) are known to suffer from low electron and hole wavefunction overlap due to high piezoelectric field. Staggered InGaN quantum wells (QWs) have been proposed to increase the wavefunction overlap and improve the efficiency of LEDs especially for long wavelength emitters. In this work we evidence that the growth of staggered QWs has also another beneficial effect as it allows to reduce the formation of defects, responsible for nonradiative Shockley-Read-Hall recombination, at the bottom interface of the QW. Staggered QWs comprised an InGaN layer of an intermediate In content between the barrier and the QW. We show that insertion of such a layer results in a significant increase of the luminescence intensity, even if the calculated wavefunction overlap drops. We study the dependence of the thickness of such an intermediate In content layer on photoluminescence (PL) intensity behavior. Staggered QWs exhibit increased cathodoluminescence (CL) homogeneity that is a fingerprint of lower density of defects, in contrast to standard QWs for which high density of dark spots are observed in QW emission mapping. Transmission electron microscopy of standard QWs revealed formation of basal-plane stacking faults (BSFs) and voids that could have resulted from vacancy aggregation. Stepwise increase of the In content in staggered QWs prevents formation of point defects and results in an increased luminescence efficiency. The In composition difference between the barrier and the well is therefore a key parameter to control the formation of point defects in the high-In content QWs, influencing the luminescence efficiency.

physics.optics↗

arXiv2022

Polarization doping ab initio verification of the concept charge conservation and nonlocality

In this work, we study the emergence of polarization doping in AlxGa1-xN layers with graded composition from a theoretical viewpoint. We demonstrate that the charge conservation law applies for fixed and mobile charges separately, leading to nonlocal compensation phenomena involving bulk fixed and mobile charge and polarization sheet charge at the heterointerfaces. The magnitude of the effect allows obtaining technically viable mobile charge density for optoelectronic devices without impurity doping (donors or acceptors). Therefore, it provides an additional tool for the device designer, with the potential to attain high conductivities: high carrier concentrations can be obtained even in materials with high dopant ionization energies, and the mobility is not limited by scattering at ionized impurities.

cond-mat.mtrl-sci↗

arXiv2022

Electrically pumped blue laser diodes with nanoporous bottom cladding

We demonstrate electrically pumped III-nitride edge-emitting laser diodes (LDs) with nanoporous bottom cladding. The LD structure was grown by plasma-assisted molecular beam epitaxy. Highly doped 350 nm thick GaN:Si cladding layer with Si concentration of 6 x 1019 cm-3 was electrochemically etched to obtain porosity of 15 +/- 3% with pore size of 20 +/- 9 nm. The devices with nanoporous bottom cladding are compared to the refer-ence structures. The pulse mode operation was obtained at 448.7 nm with a slope efficiency (SE) of 0.2 W/A while the reference device without etched cladding layer was lasing at 457 nm with SE of 0.56 W/A. The de-sign of the LDs with porous bottom cladding was modelled theoretically. Performed calculations allowed to choose the optimum porosity and thickness of the cladding needed for the desired optical mode confinement and reduced the risk of light leakage to the substrate and to the top-metal contact. This demonstration opens new possibilities for the fabrication of III-nitride LDs.

physics.app-ph↗

arXiv2018

Highly efficient optical transition between excited states in wide InGaN quantum wells

There is a lack of highly efficient light emitting devices (LEDs) operating in the green spectral regime. The devices based on (In,Al)GaN show extremely high efficiencies in violet and blue colors but fall short for longer emission wavelengths due to the quantum confined Stark effect (QCSE). In this paper we present a design of the active region based on wide InGaN quantum wells (QWs) which do not suffer from QCSE and profit from an enhancement in the internal quantum efficiency (IQE). The design exploits highly efficient optical transitions between excited states. It is shown that, counterintuitively, the devices with higher InGaN composition exhibit a higher enhancement in IQE. Experimental evidence is provided showing a gradual change in the nature of the optical transition with increasing thickness of the QW. Moreover, optical gain in long wavelength LDs incorporating standard and wide QWs is investigated to show the utilization of our concept.

physics.app-ph↗