Temperature-dependent Photoluminescence Measurements Research Articles

Anti-reflective and luminescent GaAs/AlGaAs core–shell nanowires on Si wafer with 1 ns carrier lifetime up to 400 K

We investigated the structural and optical properties of GaAs/Al0.8Ga0.2As core–shell nanowires (NWs) grown on a 2-in. Si wafer. The NWs exhibit low reflectance (<2%) across the visible to near-infrared range, attributed to their complex structure, intrinsic GaAs absorption, and a uniform NW density of approximately 3 × 108 cm−2 with an average length of 5 μm. Optical analyses based on Kubelka–Munk transformation and Tauc plot revealed minimal deviation between the estimated bandgap and the photoluminescence (PL) peak position. Temperature-dependent PL measurements between 300 and 400 K showed a weak intensity reduction and a characteristic temperature of 170 K, indicating stable emission properties within this range. Time-resolved-PL measurements demonstrated carrier lifetimes exceeding 1 ns up to 400 K, with a surface recombination velocity comparable to high-quality GaAs/AlGaAs NWs. These findings provide key insights into the optical performance and thermal stability of the NWs, highlighting their potential for optoelectronic devices operating at elevated temperatures.

Efficient and Stable Deep-Blue 0D Copper-Based Halide TEA2Cu2I4 with Near-Unity Photoluminescence Quantum Yield for Light-Emitting Diodes.

Achieving deep-blue light with high color saturation remains a critical challenge in the development of white light-emitting diode (LED) technology, necessitating luminescent materials that excel in efficiency, low toxicity, and stability. Here, we report the synthesis of [N(C2H5)4]2Cu2I4 (TEA2Cu2I4) single crystals (SCs), which exhibit deep-blue photoluminescence (PL) at 450 nm. These crystals are characterized by a significant Stokes shift of 180 nm, a long lifetime of 1.7 μs, and an impressive photoluminescence quantum yield (PLQY) of 96.7% for SCs and 87.2% for polycrystalline films. The zero-dimensional structure is attributed to the proper spacing of triangular inorganic units [Cu2I4]2- by organic cations [N(C2H5)4]+. This structural arrangement facilitates broadband deep-blue light emission with phosphorescent characteristics, as evidenced by temperature-dependent PL and time-resolved photoluminescence (TRPL) measurements. The band gap properties of TEA2Cu2I4 were further elucidated through density functional theory (DFT) computations. Notably, the material exhibited minimal PL intensity degradation after continuous UV irradiation and one month of exposure to ambient conditions. Moreover, the polycrystalline film of TEA2Cu2I4 maintained substantial deep-blue emission even after one year of storage. Utilizing TEA2Cu2I4 thin film, we fabricated an electroluminescent device emitting deep-blue light with high color saturation, featuring CIE coordinates (0.143, 0.076) and a brightness of 90 cd/m2. The exceptional photophysical properties of TEA2Cu2I4 render it a highly promising candidate for optoelectronic applications.

Eu3+- activated Sr2GdF7 colloid and nano-powder for horticulture LED applications

A series of multifunctional Sr2Gd1-xEuxF7 (x = 0, 0.05, 0.10, 0.40, 0.60. 0.80, and 1.00) phosphors in stable colloidal form and as nanopowders have been prepared using a hydrothermal method. Powder X-ray diffraction analysis confirmed that the materials crystallize in a cubic crystal structure. Transmission electron microscopy shows quasi-spherical nanoparticles with an average particle size of ∼24 nm. Photoluminescence measurements show highly efficient red emission in both colloids and nanopowders, with intensity continually increasing up to 80 mol% of Eu3+ content without concentration quenching. The most prominent emission peaks are around 600 nm (orange/red) and 700 nm (deep red), with the latter more pronounced. Quantum efficiency follows a similar trend, and reaches 60 % for the sample with 80 mol% of Eu3+ content. In addition, similar asymmetry ratio values and CIE coordinates show that there is not a big change in the local symmetry around Eu3+ ions or emission color across the series. This confirms that Eu3+ resides in the same crystalline environment in samples. The observed 5D0-level lifetimes gradually decrease from 12.0 ms to 6.9 ms as the Eu3+ concentration increases. Judd-Ofelt parameters show slight variation with Eu3+ concentration with Ω4 always larger than Ω2. The temperature-dependent steady-state and time-resolved photoluminescence measurements demonstrate high stability of nanopowders’ emission up to 100 °C. The combination of temperature stability and high efficiency of emission, as well as the untypical dominant deep-red emission at 700 nm labels these nanoparticles as potential nanophosphors for various applications.

Top-down approach for the preparation of Au/ZnO nanostructures by glancing-angle ion irradiation: Morphological, structural and optical studies

We report the 100 keV glancing-angle Xe+ ions irradiation based top down approach for the preparation of ZnO and Au/ZnO hybrid nanostructures and its morphological, structural and optical properties. FESEM micrographs reveal Xe+ ion irradiation favours the nucleation and formation of highly aligned, dense nanostrips like structures. Crystalline structure of ZnO, Xe+ ions irradiated ZnO and Au/ZnO hybrid nanostructures were analysed by grazing incident X-ray diffraction and Raman scattering measurements. The elemental compositions and thickness of the grown nanostructures were estimated using Rutherford backscattering spectrometry analysis. The influence of Xe+ ion irradiation on the photoluminescence (PL) behaviour of ZnO and Au/ZnO hybrid nanostructures were studied in detail using temperature dependent PL measurements in the range of 80–298 K. Strong PL emission associated with free excitons (FX) and its longitudinal optical phonon replicas observed in ion irradiated Au/ZnO hybrid nanostructures clearly reveal the strong coupling of the localized surface plasmons in the Au nanoparticles to the FX in ZnO. Our experimental results reveal ion beam irradiation is one of the effective approaches to tailor the optical properties of ZnO and Au/ZnO hybrid nanostructures.

High temperature photoluminescence dependence and energy migration of Tb3+-Incorporated K3Y(BO2)6 phosphors

This study investigates the structural and photoluminescence (PL) characteristics of Tb3+-incorporated K3Y(BO2)6 (KYBO) phosphors synthesized via a microwave-assisted sol-gel technique. X-ray diffraction (XRD) and Rietveld refinement confirmed the formation of a pure hexagonal phase, with lattice expansion due to Tb³⁺ doping. PL studies revealed strong green emissions centered at 541 nm, attributed to the ⁵D₄ → ⁷F₅ transitions of Tb³⁺ ions, with the highest intensity observed at 5 wt% Tb³⁺. A decrease in emission was observed at higher concentrations due to concentration quenching. Temperature-dependent PL measurements revealed reverse thermal quenching enhancing PL intensity. Chromaticity analysis based on CIE 1931 coordinates showed stable green emission across all concentrations, with a maximum color purity of 89.74% observed for the KYBO:3 wt% Tb³⁺ sample. The results, along with reverse thermal quenching behavior observed between 470K and 550K, suggest that these phosphors exhibit excellent potential for lighting and display technologies.

Different temperature-dependent fluorescence properties of CsPbBr3 nanorods and nanowires

Abstract The morphology of totally inorganic metal halide perovskites has a certain influence on their optoelectronic properties. In this study, one-dimensional CsPbBr3 nanorods (NRs) and nanowires (NWs) were arranged utilizing a boiling injection strategy. By controlling the processing time, NRs with a length of roughly 63 nm and NWs with a length of 300 nm were obtained, and it was found that the nanowires were grown from the nanorods. Temperature-dependent photoluminescence (PL) measurements were conducted on CsPbBr3 NRs and NWs, and NRs exhibit a more stable excitonic state at high temperatures (>240 K). This study provides a method to change the morphology of one-dimensional metal halide perovskite nanomaterials without doping, further promoting the application of one-dimensional all-inorganic perovskite materials in the field of optoelectronics.

Strain-induced modulation of the band structure of GaAs/GaSb/GaAs core-dual-shell nanowires

The amalgamation of high-strained core/shell geometries in nanowire (NW) heterostructures with bandgap engineering enables the systems with novel transport and optical properties. Herein, the lattice-mismatch-high construction GaAs/GaSb/GaAs core-dual-shell (CDS) NWs were grown by molecular beam epitaxy (MBE), with a focus on exploring the impact of strain on their bandgap characteristics. Interestingly, the high stain between GaSb and GaAs leads to the surface roughening that favors Stranski-Krastanov (SK) mode growth, and coherent GaSb islands on GaAs NWs form plastically relaxed mounds at the edges of the NW sidewall facets. Strain properties of GaAs/GaSb/GaAs CDS NWs have been investigated systematically by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and Raman spectra. It is clearly revealed that the presence of different strains, with the strain diminished of GaSb shell layer in the large-scale NWs and amplified in the small-scale NWs. The optical properties of the GaAs/GaSb/GaAs CDS NWs were investigated by power- and temperature-dependent photoluminescence (PL) measurements, which reveal the emission properties with the exciton localization phenomenon. Our results on the unique optical properties of localized excitons in GaAs/GaSb/GaAs core-shell nanostructures open the way to the design of stable optoelectronic devices.

Influence of Ce3+ Doping on Photoluminescence Properties and Stability of Cs4SnBr6 Zero-Dimensional Perovskite

Zero-dimensional tin-based halide perovskites have garnered considerable interest owing to their remarkable optical properties, including broad-band emission, high photoluminescence (PL) efficiency, and low self-absorption. Nevertheless, enhancing the PL efficiency and stability of these materials remains a pressing challenge. In this study, the enhancement of PL and stability in Cs4SnBr6 zero-dimensional perovskite was investigated through Ce3+ doping. Our experimental results demonstrate that the incorporation of Ce3+ can significantly boost the light emission intensity from self-trapped excitons (STEs) in Cs4SnBr6, achieving over a 150% increase compared to the undoped sample, with a PL quantum yield of approximately 64.7%. Moreover, the thermal stability of the corresponding doped sample is markedly enhanced. Through comprehensive analyses, including X-ray diffraction, energy-dispersive spectroscopy, time-resolved PL, and temperature-dependent PL measurements, we elucidate that the enhanced light emission is attributed to the distortion of the [SnBr6]4− octahedral structure induced by Ce3+ doping, which strengthens electron–phonon coupling and elevates the binding energy of STEs.

Lead-Free Cs2AgBiCl6 Double Perovskite: Experimental and Theoretical Insights into the Self-Trapping for Optoelectronic Applications.

Lead-free double perovskites (DPs) will emerge as viable and environmentally safe substitutes for Pb-halide perovskites, demonstrating stability and nontoxicity if their optoelectronic property is greatly improved. Doping has been experimentally validated as a powerful tool for enhancing optoelectronic properties and concurrently reducing the defect state density in DP materials. Fundamental understanding of the optical properties of DPs, particularly the self-trapped exciton (STEs) dynamics, plays a critical role in a range of optoelectronic applications. Our study investigates how Fe doping influences the structural and optical properties of Cs2AgBiCl6 DPs by understanding their STEs dynamics, which is currently lacking in the literature. A combined experimental-computational approach is employed to investigate the optoelectronic properties of pure and doped Cs2AgBiCl6 (Fe-Cs2AgBiCl6) perovskites. Successful incorporation of Fe3+ ions is confirmed by X-ray diffraction and Raman spectroscopy. Moreover, the Fe-Cs2AgBiCl6 DPs exhibit strong absorption from below 400 nm up to 700 nm, indicating sub-band gap state transitions originating from surface defects. Photoluminescence (PL) analysis demonstrates a significant enhancement in the PL intensity, attributed to an increased radiative recombination rate and higher STE density. The radiative kinetics and average lifetime are investigated by the time-resolved PL (TRPL) method; in addition, temperature-dependent PL measurements provide valuable insights into activation energy and exciton-phonon coupling strength. Our findings will not only deepen our understanding of charge carrier dynamics associated with STEs but also pave the way for the design of some promising perovskite materials for use in optoelectronics and photocatalysis.

Probing the Band Splitting near the Γ Point in the van der Waals Magnetic Semiconductor CrSBr.

This study investigates the electronic band structure of chromium sulfur bromide (CrSBr) through comprehensive photoluminescence (PL) characterization. We clearly identify low-temperature optical transitions between two closely adjacent conduction-band states and two different valence-band states. The analysis on the PL data robustly unveils energy splittings, band gaps, and excitonic transitions across different thicknesses of CrSBr, from monolayer to bulk. Temperature-dependent PL measurements elucidate the stability of the band splitting below the Néel temperature, suggesting that magnons coupled with excitons are responsible for the symmetry breaking and brightening of the transitions from the secondary conduction band minimum (CBM2) to the global valence band maximum (VBM1). Collectively, these results not only reveal splitting in both the conduction and valence bands but also highlight a significant advance in our understanding of the interplay between the optical, electronic, and magnetic properties of antiferromagnetic two-dimensional van der Waals crystals.

Excitonic emission and phonon anharmonicity in Cs3Sb2Br9

We investigate emission characteristics, phonon–phonon, and electron–phonon interactions in a lead-free halide perovskite Cs3Sb2Br9 through temperature-dependent photoluminescence, Raman scattering, and x-ray diffraction measurements. The exciton–optical phonon coupling leads to below bandgap broad emissions, arising from self-trapped excitons recombination. The anomalous temperature dependence of the lowest frequency Raman mode is attributed to the phonon–phonon and electron–phonon interactions. The temperature-dependent x-ray diffraction measurement reveals a minimum in the volume thermal expansion coefficient at around 120 K. We also quantify the quasiharmonic contributions to the phonon frequency shift for all Raman modes.

Tailoring structural ordering and optical characteristics of In0.49Ga0.51P films via Zn doping engineering by MOCVD

In0.49Ga0.51P is highly promising due to its favorable lattice-matching properties with GaAs, making it well-suited for various device applications. This study investigated the influence of Zn doping on the ordering and optical properties of In0.49Ga0.51P grown on GaAs using metalorganic chemical vapor deposition. By precisely controlling the doping flow, the ordering degree of In0.49Ga0.51P was systematically modulated. The luminescence origin and bandgap characteristics of In0.49Ga0.51P were examined through temperature-dependent photoluminescence and Hall measurements. The findings demonstrate a noticeable peak shift, accompanied by a increase in the bandgap and a corresponding decrease in the ordering degree as the Zn concentration increases.

The Influence Mechanism of Quantum Well Growth and Annealing Temperature on In Migration and Stress Modulation Behavior.

This study explores the effects of growth temperature of InGaN/GaN quantum well (QW) layers on indium migration, structural quality, and luminescence properties. It is found that within a specific range, the growth temperature can control the efficiency of In incorporation into QWs and strain energy accumulated in the QW structure, modulating the luminescence efficiency. Temperature-dependent photoluminescence (TDPL) measurements revealed a more pronounced localized state effect in QW samples grown at higher temperatures. Moreover, a too high annealing temperature will enhance indium migration, leading to an increased density of non-radiative recombination centers and a more pronounced quantum-confined Stark effect (QCSE), thereby reducing luminescence intensity. These findings highlight the critical role of thermal management in optimizing the performance of InGaN/GaN MQWs in LEDs and other photoelectronic devices.

Manipulating the phase stability of a halide perovskite, CH3NH3PbI3 by high-pressure cycling

Methylammonium lead iodide perovskite, CH3NH3PbI3 (MAPbI3) is a highly promising photovoltaic material, whose structural and electronic properties are very sensitive to applied stresses. Here, we show that the phase stability of a MAPbI3 crystal can be controlled by structural defects and strains. We synthesized a single crystal of MAPbI3 and measured its electrical properties across two successive structural phase transitions under applied pressure up to 4–9 GPa under multiple high-pressure cycling. We revealed three types of effects of this high-pressure treatment. (i) An increasing the level of defects and strains in the crystal greatly delays the first reconstructive phase transition, conserving the ambient-pressure tetragonal phase up to a record pressure of ∼1.4 GPa, much higher compared to its typical stability range of up to 0.3–0.5 GPa only. (ii) A time exposure of the crystal at a fixed pressure corresponding to the beginning of the second phase transition to a “destabilized” structure eliminated some of defects and strains; it down-shifted the phase boundaries back. (iii) A recrystallization of the sample after pressure-induced amorphization enhanced its structural stability against amorphization upon subsequent pressurization cycle. We proposed that the most abundant defects and strains, which could appear in the pressure-cycled MAPbI3 crystals, were related to migration of iodine atoms from their regular sites to the MA interstices. Temperature-dependent photoluminescence measurements indicated that the sample recovered after the high-pressure cycling crystallized back into the initial tetragonal crystal structure. Whereas, its stability range expanded toward lower temperatures by 20 K and a band gap slightly increased, from 1.59 to 1.625 eV (at 290 K). Using this organic-inorganic perovskite as an example, we show how the phase stability of such materials can be manipulated by creation and elimination of structural defects and local strains.

The impact of laser lift-off with sub-ps pulses on the electrical and optical properties of InGaN/GaN light-emitting diodes

Laser lift-off (LLO) is an important step in the processing chain of nitride-based light-emitting diodes (LEDs), as it enables the transfer of LEDs from the growth substrate to a more suitable carrier. A distinctive feature of LLO with ultrashort pulses is the ability to use either above- or below-bandgap radiation, since nonlinear absorption becomes relevant for ultrashort pulses. This study addresses the differences in the absorption scheme for below- and above-bandgap radiation and investigates the electrical and optical properties of InGaN/GaN LEDs before and after LLO with 347 and 520 nm laser light via current–voltage and power- as well as temperature-dependent photoluminescence measurements. LLO could be successfully realized with both wavelengths. The threshold fluence required for LLO is about a factor of two larger for 520 nm compared to that for 347 nm. Furthermore, an increase in leakage current by several orders of magnitude and a significant decrease in efficiency with laser fluence are observed for below-bandgap radiation. In contrast, leakage current hardly increases and efficiency is less dependent on the laser fluence for samples lifted with 347 nm. This degradation is ascribed to the absorption of laser light in the active region, which facilitates a modification of the local defect landscape. The effect is more severe for below-bandgap radiation, as more laser light penetrates deep into the structure and reaches the active region. Ultimately, we show that LEDs lifted with ultrashort laser pulses can exhibit good quality, making ultrashort pulse LLO a viable alternative to conventional LLO with nanosecond pulses.

Strong Exciton-Phonon Coupling as a Fingerprint of Magnetic Ordering in van der Waals Layered CrSBr.

The layered, air-stable van der Waals antiferromagnetic compound CrSBr exhibits pronounced coupling among its optical, electronic, and magnetic properties. As an example, exciton dynamics can be significantly influenced by lattice vibrations through exciton-phonon coupling. Using low-temperature photoluminescence spectroscopy, we demonstrate the effective coupling between excitons and phonons in nanometer-thick CrSBr. By careful analysis, we identify that the satellite peaks predominantly arise from the interaction between the exciton and an optical phonon with a frequency of 118 cm-1 (∼14.6 meV) due to the out-of-plane vibration of Br atoms. Power-dependent and temperature-dependent photoluminescence measurements support exciton-phonon coupling and indicate a coupling between magnetic and optical properties, suggesting the possibility of carrier localization in the material. The presence of strong coupling between the exciton and the lattice may have important implications for the design of light-matter interactions in magnetic semiconductors and provide insights into the exciton dynamics in CrSBr. This highlights the potential for exploiting exciton-phonon coupling to control the optical properties of layered antiferromagnetic materials.

Low Surface Recombination in Hexagonal SiGe Alloy Nanowires: Implications for SiGe-Based Nanolasers.

Monolithic integration of silicon-based electronics and photonics could open the door toward many opportunities including on-chip optical data communication and large-scale application of light-based sensing devices in healthcare and automotive; by some, it is considered the Holy Grail of silicon photonics. The monolithic integration is, however, severely hampered by the inability of Si to efficiently emit light. Recently, important progress has been made by the demonstration of efficient light emission from direct-bandgap hexagonal SiGe (hex-SiGe) alloy nanowires. For this promising material, realized by employing a nanowire structure, many challenges and open questions remain before a large-scale application can be realized. Considering that for other direct-bandgap materials like GaAs, surface recombination can be a true bottleneck, one of the open questions is the importance of surface recombination for the photoluminescence efficiency of this new material. In this work, temperature-dependent photoluminescence measurements were performed on both hex-Ge and hex-SiGe nanowires with and without surface passivation schemes that have been well documented and proven effective on cubic silicon and germanium to elucidate whether and to what extent the internal quantum efficiency (IQE) of the wires can be improved. Additionally, time-resolved photoluminescence (TRPL) measurements were performed on unpassivated hex-SiGe nanowires as a function of their diameter. The dependence of the surface recombination on the SiGe composition could, however, not be yet addressed given the sample-to-sample variations of the state-of-the-art hex-SiGe nanowires. With the aforementioned experiments, we demonstrate that at room temperature, under high excitation conditions (a few kW cm-2), the hex-(Si)Ge surface is most likely not a bottleneck for efficient radiative emission under relatively high excitation conditions. This is an important asset for future hex(Si)Ge optoelectronic devices, specifically for nanolasers.

Structural, photoluminescence and energy transfer investigations of novel Dy3+ → Sm3+ co-doped NaCaPO4 phosphors for white-light-emitting diode applications.

In this study, Dy3+-doped and Dy3+/Sm3+ co-doped NaCaPO4 white-emitting polycrystalline phosphor samples were synthesized using a solid-state reaction method. The samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field-emission scanning electron microscopy (FE-SEM), and Photoluminescence (PL) analysis. The phase purity characterization and crystal structural analysis were done using the Rietveld refinement-based FullProf Suite software. The Rietveld refinement result confirms single-phase formation for both Sm3+ and Dy3+/Sm3+ co-doped NaCaPO4 samples with an orthorhombic structure and with a monotonic change in lattice parameters with doping. The PL studies of the Dy3+-doped samples revealed two emission bands. However, at 352 nm, the Dy3+/Sm3+-co-doped samples revealed distinctive emission bands for both ions. The emission peaks at 480 nm (blue) and 573 nm (yellow) are related to the 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+ ions; however, the emission peaks at 600 nm and 647 nm are attributed to the 4G5/2 → 6H7/2 and 4G5/2 → 6H7/2 transitions of Sm3+ ions. The intensity of the Dy3+ emissions decreased as the Sm3+ levels increased but the emission intensity of the Sm3+ ions increased. The co-doping of Sm3+ ions in Dy3+-doped phosphors results in unique characteristics due to the energy transfer (ET) from Dy3+ → Sm3+ ions. The effectiveness of this ET from Dy3+ → Sm3+ ions is positively correlated with the dopant amounts of the Sm3+ ions. The interaction mechanisms have been identified as dipole-dipole based on Dexter's energy transfer and Readfield's approaches. All decay curves can be adequately fitted via bi-exponential functions, suggesting the movement of energy between Dy3+ → Sm3+ ions. Temperature-dependent PL measurements and CIE color coordinate analysis reveal excellent luminescent properties, making these Dy3+/Sm3+ co-doped phosphors advantageous for white light-emitting diode (WLED) technologies.

On the unique temperature-dependent interplay of a B-exciton and its trion in monolayer MoSe2.

Plasmonics in metal nanoparticles can enhance their near field optical interaction with matter, promoting emission into selected optical modes. Here, using Ga nanoparticles with carefully tuned plasmonic resonance in proximity to MoSe2 monolayers, we show selective photoluminescence enhancement from the B-exciton and its trion with no observable A-exciton emission. The nanoengineered substrate allows for the first direct experimental observation of the B-trion binding energy in semiconducting monolayers. Using temperature-dependent photoluminescence measurements, we show the following features of the MoSe2 B-exciton family: (i) the trion binding energy has an observable temperature dependence with a decreasing trend towards low temperatures and (ii) the exciton-trion emission ratio varies non-monotonically with temperature with a steep increase in the trion emission at lower temperatures. Using detailed models, we identify the particle size required for selective excitation and describe the underlying physical processes. This opens newer avenues for selectively promoting excitonic species and tuning the effective particle lifetimes in monolayer semiconductors. These results demonstrate the excellent plasmonic properties of Ga nanoparticles, which along with facile processing techniques makes it an attractive alternative to the prevalent noble metal plasmonics having applications in flexible/stretchable materials and textiles.

Effects of parabolic barrier design for multiple GaAsBi/AlGaAs quantum well structures

The results of a comparative study on how the design of multiple quantum structures containing a parabolic barrier profile affects optical properties are presented. All quantum well (QW) structures were grown by molecular beam epitaxy (MBE) on semi-insulating GaAs substrates. The investigated samples consisted of (i) double parabolic quantum wells (type A) or (ii) multiple (two or three) rectangular quantum wells surrounded by parabolic barriers (type B). The optical quality of samples was characterized performing room-temperature (RT-PL) and temperaturedependent photoluminescence (TD-PL) measurements. The investigation aimed at the optimization of a multiple quantum well (MQW) structure design for application in the gain region of near infrared (NIR) laser diodes (LDs) revealed benefits of both double parabolic quantum wells and a mixed design (rectangular MQW with parabolic barriers). The PL band position for all samples was registered in the vicinity around 1.19 eV, which corresponds to the Bi content in QW of ~4.4%. It was shown that all structures of type A exhibit an intense emission, while the intensity of photoluminescence measured for the samples of type B depends on the number of QWs. The weaker intensity of the PL signal from two QWs inserted between parabolic barriers was explained by a larger point defect density at low temperature grown inner GaAs barriers. The room-temperature PL intensity of the structure with three GaAsBi QWs embedded in one parabolic AlGaAs barrier was the highest one. The shift of PL peak position to lower energies (1.16 eV) was attributed to the slightly higher bismuth concentration, 4.9%.