Group-IV GeSn alloys have gained significant attention as an attractive material system for silicon photonics. Thermal annealing provides an efficient route to improve the crystalline quality and overall performance of GeSn layers. Here, we present a comparative study on the effects of rapid thermal annealing (RTA) and microwave annealing (MWA) on GeSn samples grown on Si via Ge buffer layers containing '6.3% Sn under a compressive strain of 0.793%. Structural analysis reveals that RTA at '380 degrees C yields a modest strain relaxation of '20% and enhanced crystallinity. However, RTA at higher temperatures results in defect generation and a decrease in photoluminescence (PL) emission intensity. In contrast, MWA at a moderate power of '900 W achieves a higher strain relaxation of '27-28% while preserving both material quality and PL emission. This advantage is attributed to the more localized energy delivery and reduced thermal budget of MWA, which mitigates Sn diffusion and maintains alloy integrity. In addition, theoretical analysis of the strain-dependent band structure and spontaneous emission in GeSn further confirms that increased strain relaxation enhances the direct-gap character and radiative recombination. These findings demonstrate that MWA offers a more robust and scalable post-growth annealing route for optimizing GeSn layers while balancing strain engineering, optical performance, and material stability, thereby advancing the development of high-performance, complementary metal oxide semiconductor-compatible GeSn-based photonic devices. (c) 2026 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

The optical performance of nitride-based heterostructures that spontaneously emit light in the deep-ultraviolet range (wavelengths below 230 nm) is limited by various previously elucidated phenomena related to the details of the valence band structure, the need to resolve various technological issues with a view to improving electrical injection, and the need to address light extraction issues. In this article, we compare the light-matter interaction strategy in high-quality multiple quantum wells developed by both molecular beam epitaxy and organometallic vapor phase epitaxy, using temperature-dependent photoluminescence measurements performed in the range 8-300 K. The deterioration of light emission between 8 and 300 K is governed by two recombination mechanisms operating at low temperatures (below approximately 100 K) and at higher temperatures, respectively. The efficiency of the non-radiative recombination channel at low temperatures is extrinsic in origin; it is mediated by impurities and by the density of defects in the crystal. The second process is intrinsic in nature and is related to the thermal ionization of excitons at higher temperatures. We believe that the ultimate solution to partially reduce these phenomena could be homoepitaxy on high-quality AlN substrates.

Group-IV GeSn alloys have gained significant attention as an attractive material system for silicon photonics. Thermal annealing provides an efficient route to improve the crystalline quality and overall performance of GeSn layers. Here, we present a comparative study on the effects of rapid thermal annealing (RTA) and microwave annealing (MWA) on GeSn samples grown on Si via Ge buffer layers containing ∼6.3% Sn under a compressive strain of 0.793%. Structural analysis reveals that RTA at ∼380 °C yields a modest strain relaxation of ∼20% and enhanced crystallinity. However, RTA at higher temperatures results in defect generation and a decrease in photoluminescence (PL) emission intensity. In contrast, MWA at a moderate power of ∼900 W achieves a higher strain relaxation of ∼27–28% while preserving both material quality and PL emission. This advantage is attributed to the more localized energy delivery and reduced thermal budget of MWA, which mitigates Sn diffusion and maintains alloy integrity. In addition, theoretical analysis of the strain-dependent band structure and spontaneous emission in GeSn further confirms that increased strain relaxation enhances the direct-gap character and radiative recombination. These findings demonstrate that MWA offers a more robust and scalable post-growth annealing route for optimizing GeSn layers while balancing strain engineering, optical performance, and material stability, thereby advancing the development of high-performance, complementary metal oxide semiconductor-compatible GeSn-based photonic devices.

In this work, we systematically investigate the effects of metal doping on the structural, electrical, and optical properties of spin-coated nanocrystalline ZnO thin films prepared by a simple acetate-based solution process. The incorporation of different metal dopants significantly modified the crystallographic, electrical, and photoluminescence properties of ZnO. Doping with alkali metals enhanced the photoluminescence efficiency and enabled amplified spontaneous emission, whereas Mg was the only dopant that produced a pronounced blue shift in the photoluminescence spectra. Lithium-doped ZnO exhibited a strong concentration-dependent electrical behavior, producing highly conductive n-type ZnO at a 1% doping level and p-type conductivity at an 8% concentration. Strong n-type conductivity was also achieved using low concentrations of Li and Na and higher concentrations of Al. In contrast, Fe-, Ni-, Cu-, and Pb-doped ZnO exhibited a substantial reduction in electrical conductivity accompanied by strong photoluminescence quenching, indicating enhanced defect-related carrier compensation. These results demonstrate that metal doping provides an effective approach for tailoring the structural, optical, and electrical properties of ZnO and offers a versatile route toward engineering ZnO-based layers for optoelectronic devices, transparent conductive contacts, photodetectors, solar cells, and ultraviolet laser applications.

We develop CsxFA1-xPbI3 perovskite photodetectors with varying Cs content in the x = 0.05-0.25 range to identify the most stable cubic-lattice perovskite composition for visible-light photodetection. The perovskite layers were deposited by the spin-coating technique on a nickel oxide p-type contact and then were covered with C60/Ag electron contact to obtain a vertical pin diode structure. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements show that x = 0.1-0.2 provides the most stable lattice and pinhole-free perovskite layers. The photocurrents are linear in an extremely wide 1 nW-10 mW excitation power range, providing photoresponsivity of 0.28 A/W at 532 nm (green light), similar to that of Si photodiodes. The testing of the photodetectors using picosecond pulses provided their rise times and fall times. The x = 0.2 composition provided the shortest rise time values of 27.5 ns, leading to a detector modulation bandwidth of 12.7 MHz. This indicates that this perovskite composition is suitable for replacing silicon photodetectors in cost-efficient light detection systems for imaging and light communication applications such as Li-Fi.

A new ternary La-Bi-Pb alloy system was developed to improve resistance to atmospheric oxidation, with lanthanum content in the range of 10-22 wt%. A Pb-Bi eutectic alloy was used as a solvent for La at approximately 400 degrees C in a nitrogen atmosphere. Structural and compositional analysis of the solid-state alloys was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The results show the formation of Bi2La phases at significantly lower temperatures in the presence of Pb. CALPHAD calculations provide a consistent description of the experimentally observed redistribution of elements. Electrical and magnetotransport measurements reveal measurable positive magnetoresistance and allow evaluation of the alloy stability under ambient conditions through time-dependent conductivity changes.

Irradiation of a pure Sn wafer with a nanosecond pulsed Nd:YAG laser with different intensities from 2 GW/cm2 to 6 GW/cm2 and a wavelength of λ=1.06 μm leads to the formation of SnO thin films with different thicknesses and unique optical properties. Photoluminescence (PL) spectra, PL relaxation spectra, and Raman light backscattering spectra were used to study the optical properties, crystallinity, and phase composition of the films. Optical microscopy and UV photoluminescence were used to study the size, position, and visualization of the SnO film. Laser emission from a thin SnO film was first observed by excitation with a femtosecond laser with a wavelength of λexc=266 nm on the exciton band with λ=390 nm. The film was formed under the action of Nd:YAG laser with an intensity of 6 GW/cm2. Laser radiation is characterized by both the threshold excitation energy density - fluence Fthr=0.8 mJ/cm2, and the Purcell factor FP=50, measured during femtosecond laser excitation of photoluminescence with a femtosecond laser with a wavelength of λexc=266 nm.

High-quality perovskite films are essential for developing efficient planar perovskite solar cells (PSCs). However, as-prepared perovskite films typically exhibit low crystallinity and high trap densities, leading to degraded performance in PSCs. Moreover, the challenge of creating low-toxicity, high-performance mixed Zn/Pb halide perovskite solar cells at a reduced cost remains significant. In the present work, Zinc (Zn) was introduced as a cation substitute for the toxic lead (Pb) in the CsZnxPb1-xI3 perovskite compound (x = 0.3-0.7), leveraging its non-toxic nature, oxidation resistance, and earth abundance. The structural and photovoltaic properties of Zn-alloyed Pb/Zn hybrid perovskite solar cells (PSCs) produced by a simple spin-coating process from non-colloidal precursor solution are further investigated. The results demonstrate that a heavily 45 % Zn-alloyed perovskite significantly enhances crystal quality, surface coverage, and grain size while reducing the non-radiative recombination by increasing carrier lifetime and diffusion length. These improvements led to enhanced photovoltaic performance. Specifically, the CsZn0.45Pb0.55I3 solar cells demonstrated the highest performance with minimal Pb content, exhibiting an open-circuit voltage (Voc) of 1.04 V and a short-circuit current density (Jsc) of 18.7 mA/cm2. The performance of the CsZn0.5Pb0.5I3 solar cells was found to vary with light intensity, showing changes in efficiency, fill factor, Jsc,and Voc, which were explained by variation of carrier diffusion coefficients and recombination lifetime due to trapping and recombination processes.

We demonstrate structural color generation in silicon-on-insulator wafers using nanosecond laser irradiation. Laser-induced periodic surface structures on the thin Si film act as grating couplers, enabling optical resonances that produce bright, spectrally selective structural colors at visible wavelengths. The mechanism combines grating-mediated waveguide coupling with Fabry-Perot spectral filtering, yielding optical characteristics resembling guided-mode resonance. The central wavelength is tunable across the visible spectrum by varying Si film thickness (50-70 nm range), with measured samples exhibiting green coloration at 55 nm and red at 70 nm thickness. Numerical simulations qualitatively reproduce the observed optical properties. This non-chemical, non-fading coloration offers potential applications in secure marking and process control for semiconductor manufacturing.

A new ternary La–Bi–Pb alloy system was developed to improve resistance to atmospheric oxidation, with lanthanum content in the range of 10–22 wt.%. A Pb–Bi eutectic alloy was used as a solvent for La at approximately 400 °C in a nitrogen atmosphere. Structural and compositional analysis of the solid-state alloys was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The results show the formation of Bi₂La phases at significantly lower temperatures in the presence of Pb. CALPHAD calculations provide a consistent description of the experimentally observed redistribution of elements. Electrical and magnetotransport measurements reveal measurable positive magnetoresistance and allow evaluation of the alloy stability under ambient conditions through time-dependent conductivity changes.

Metal halide perovskites (MHPs) have garnered considerable interest as alternative semiconductor‐based laser sources due to their low‐cost and low‐temperature solution processability. Among them, cesium lead iodide (CsPbI 3 ) stands out as a promising candidate for light–emitting diodes and laser applications. However, achieving long‐term structural and operational stability remains a significant challenge. In this study, CsPbI 3 is alloyed with zinc (Zn) and incorporated 3% polyvinylpyrrolidone (PVP) into the precursor solution to enhance film quality and device performance. A second‐order CsZn 0.4 Pb 0.6 I 3 thin film distributed feedback (DFB) laser is demonstrated with the grating formed directly on the perovskite by holographic lithography using Nd: YAG laser radiation. CW laser annealing of the laser‐processing damage is found beneficial for stabilizing the DFB laser output parameters. The DFB laser based on the PVP: CsZn 0.4 Pb 0.6 I 3 film exhibits a lasing threshold of 55 µJ cm − 2 at room temperature with a lasing peak centered at 709 nm in the deep‐red spectral region. Remarkably, the laser structure can maintain stable operation for over 400 million pulses, or one year if operated at a repetition rate of 10 Hz. This work represents a substantial advancement toward the realization of electrically driven perovskite lasers for future commercial applications.

Metal halide perovskites (MHPs) have garnered considerable interest as alternative semiconductor-based laser sources due to their low-cost and low-temperature solution processability. Among them, cesium lead iodide (CsPbI3) stands out as a promising candidate for light-emitting diodes and laser applications. However, achieving long-term structural and operational stability remains a significant challenge. In this study, CsPbI3 is alloyed with zinc (Zn) and incorporated 3% polyvinylpyrrolidone (PVP) into the precursor solution to enhance film quality and device performance. A second-order CsZn0.4Pb0.6I3 thin film distributed feedback (DFB) laser is demonstrated with the grating formed directly on the perovskite by holographic lithography using Nd: YAG laser radiation. CW laser annealing of the laser-processing damage is found beneficial for stabilizing the DFB laser output parameters. The DFB laser based on the PVP: CsZn0.4Pb0.6I3 film exhibits a lasing threshold of 55 mu J cm- 2 at room temperature with a lasing peak centered at 709 nm in the deep-red spectral region. Remarkably, the laser structure can maintain stable operation for over 400 million pulses, or one year if operated at a repetition rate of 10 Hz. This work represents a substantial advancement toward the realization of electrically driven perovskite lasers for future commercial applications.

Doping is used in many pn junction devices, such as polycrystalline solar cells, to increase the strength of the junction field to assist charge carrier collection and thus partially mitigate nonradiative recombination losses. We demonstrate a different doping characteristic for inorganic solar cells: using dopants to reduce charge carrier trapping and electronic band tails. Alloying CdTe with Se to form CdSeTe semiconductor reduced recombination, but CdSeTe has more complex defect states which can limit further efficiency gains due to charge carrier trapping and trap-limited mobility. Doping CdSeTe with P (but not N, As, or Sb in this study) reduces band tails (Urbach energies) and lessens the impact of the near valence band trap states, with ambipolar mobilities improving to >50 cm2V-1s-1, fill factor increasing from 76% to 79%, and efficiencies increasing by 0.9% absolute. Simulations are used to show how such defect reduction improves performance in the radiative limit.

PL-based external radiative efficiency (ERE) and implied open-circuit voltage (iV(OC)) metrics were introduced for thin-film solar absorbers to better understand the voltage deficit and diagnose losses in solar cells. Traditionally, elevated ERE and iV(OC) measurements are associated with diminished recombination within the solar device, a rationale heavily reliant on the assumption of a uniform bandgap and high carrier mobilities in the absorber. Recently, very low mobilities in CdSeTe absorbers (< 1 cm(2)/(Vs)) were measured using the light-induced transient grading technique. In this study, we use a detailed numerical model of iV(OC) to investigate the possible reasons of elevated iV(OC) in realistic CdSeTe absorbers with a graded Se profile. In particular, we examine how the bandgap nonuniformity and the reduced hole mobility in graded CdSeTe absorbers affect iV(OC) measurements. We show that high iV(OC) may result from inflated quasi-Fermi level splitting in the high-Se region in the front part of a CdSeTe absorber with slow hole transport. We reproduce the experimentally reported 360 mV increase in iV(OC)-V-OC gap with reduced doping using a model with sub-1 cm(2)/(Vs) hole mobility in the high-Se region. Based on our results, we conclude that the iV(OC) metric (or ERE metric) should not be used as a sole metric of CdSeTe absorber quality. We discuss possible ways to extract useful information from the iV(OC)-V-OC gap by supplementing the front-side illumination measurements with back-side illumination measurements.

An innovative phase field model has been considered to describe the impurity redistribution in a rapid solidification process. This model has been implemented for the description of a complex process in GeSn/Si structure, consisting of the laser heating of solid phase, melting and solidification process. It allowed us to calculate the Sn concentration profile after repeated laser pulses. A significant increase of the Sn concentration near the surface is observed due to the segregation effect accumulated over many laser pulses. The obtained results are in a qualitative agreement with the experimental data for Ge0.04Sn0.96 layer irradiated with nanosecond laser pulses. The differences between these results and those obtained earlier by the molecular beam epitaxy method are discussed.

The generation and transport parameters of charge carriers are critical for the evaluation of optoelectronic devices. In this study, we alloyed CsPbI3 perovskite by partially substituting Pb2+ with Zn2+ in a simple solution process technique. The spin-coated thin films were investigated to analyze the effect of Zn2+ substitution on the charge carrier lifetimes and diffusion coefficients. Samples with moderate levels of Zn exhibited improved morphological characteristics and a higher absorption coefficient. No significant band gap shift was observed, even in highly Zn2+-alloyed thin films. A photoluminescence (PL) lifetime of up to 710 ns was recorded in samples with 40% Zn alloying, suggesting enhanced morphology and fewer trap states. The diffusion coefficient, diffusion length, and charge carrier lifetime were measured across a wide range of excitation densities using both fast and slow light-induced transient grating (LITG) methods. At higher carrier densities, an increase in both the carrier recombination rate and diffusivity was observed. Bimolecular and Auger recombination processes were characterized by coefficients B 0 = 5-8.5 x 10-10 cm3s-1 and C = 4-8 x 10-29 cm6s-1, respectively, in 30-40% Zn-alloyed CsPbI3 samples. The LITG results indicated a direct correlation between higher carrier densities, increased diffusion coefficients (similar to 20 cm2/s), and a reduction in charge carrier lifetime, which can be attributed to carrier degeneracy and localized state saturation. The highest diffusion lengths, related to carrier density, were found in samples with similar to 40% Zn alloying. Additionally, the slow LITG method revealed a 3 orders of magnitude smaller localized exciton diffusion coefficient, which initially increased and further decreased across varying Zn concentrations. Slow LITG and PL decays showed similar lifetime values related to localized excitons, providing high PL efficiency.

We develop a rapid and spatially controlled formation method of a smooth polycrystalline SnO film preventing the transition to a more stable SnO2 phase. The phase and structural state of a SnO oxide film, which was formed by pulsed irradiation of a Nd:YAG laser on a tin plate in contact with air and distilled water, were studied. XRD, Raman spectra, and kinetics of the exciton PL under femtosecond excitation showed a more perfect textured structure and strong exciton emission of the SnO film obtained by the laser under the conditions of Sn contact with air. The obtained results indicate the applicability of the laser method for the formation of SnO layers, according to the given topology, which can be used for UV-emitting devices and photocatalysts.

The fundamental characteristics of the Coulomb e-h interactions in ultra-pure diamond are investigated through time-resolved photoconductivity measurements in homogeneously photoexcited samples with ohmic-like low resistive B+ sandwich contacts. We demonstrate that, in the electric field, the bipolar charge mobility exhibits drastic reduction for photo-injected densities of 1014-1016 cm-3 that cannot be explained only by mutual scattering between free e-h particles. This phenomenon is clarified by adding scattering caused by excitons whose density grows in the photo-exited system. The comparison of drift mobilities at 300 K in diamond obtained in this study and in pure Si and Ge obtained from literature, where exciton scattering is insignificant, is presented. We derive the empirical expression for the density dependences of bipolar mobility for the electric fields up to 1 kV/ cm that could be useful for the development of diamond electronic devices.

Interest in hexagonal boron nitride (hBN) is booming due to its exceptional properties and potential applications: including a wide bandgap that emits deep ultraviolet light, its 2D structure, and its excellent chemical and thermal stability. In this work, intralayer carrier diffusion and exciton‐exciton annihilation in hBN are investigated by time‐resolved two‐color pump‐probe experiments. Two‐photon femtosecond excitation makes it possible to monitor the carrier relaxation dynamics in hBN under conditions of negligible surface recombination. A value of the two‐photon absorption coefficient β = 1.7 ± 0.5 cm GW −1 is measured at 350 nm and its dependence in the 315–415 nm range. The obtained in‐plane exciton diffusivity increases with excitation power due to the screening of the exciton‐phonon interaction at high charge carrier densities between 10 15 and 10 17 cm −3 . Conversely, the exciton‐exciton annihilation efficiency decreases by a factor of five from 80 to 600 K. Due to these efficient Auger processes, the in‐plane diffusion length in hBN is reduced from 0.24 to 0.1 µm as the excitation density increases. The robustness of the photoluminescence intensity is mediated in the high temperature range by excitons with a binding energy of 390 meV.