Numerical study on SnSSe solar cells with the addition of quantum wells under the radiative limit for boosting device efficiency

Nondiffusing localized excitons (XL) in two-dimensional semiconductors present a robust platform for mediating light-matter interactions, with potential applications in both photovoltaics and light-emitting devices. However, at room temperature, high thermal energy hinders XL formation, while excess charges diminish the quantum yield (QY) through nonradiative decay. Here, we present high-QY XL emission in ambient conditions by removing excess charges and inducing efficient exciton funneling into a Au nanohole. Specifically, by evaporating an H2O barrier between the n-type MoS2 and the Au substrate, we induce a grounding effect on electrons. Dominantly populating excitons are then funneled and bound to the nanohole through the strain-induced zero-dimensional quantum well effect. We confirm the exciton confinement efficiency of ~98% using a drift-diffusion model, enabling bright XL emission at the nanoscale. Using tip-induced gigapascal-scale pressure, we control XL dynamics and QY in a reversible manner. Our approach provides an innovative strategy for XL-based nanophotonic devices.

Growing industrial, environmental, and healthcare needs are accelerating the development of next-generation infrared systems with high detectivity, multifunctional sensing, and on-device intelligence. While traditional devices (e.g., HgCdTe, quantum wells) continue to dominate in terms of performance, they face limitations in cooling requirements, cost, and functionality. Recently, considerable advances have been made in materials, structures, and detection systems. As the foundation of IR systems, photodetectors based on traditional materials with band alignment engineering and emerging materials (e.g., two-dimensional materials and quantum dots) show high photodetectivity, low dark current, and room-temperature operation. Meanwhile, on-chip microstructures (e.g., plasmons, metasurfaces, and 3D-assembled architectures) integration enables manipulation of coupling and propagation of electromagnetic fields, which enhances polarization and wavelength-dependent light absorption. These developments empower infrared devices with multidimensional photodetection capabilities and tunable spectral response. Furthermore, advanced technologies like in-sensor computing, miniaturized spectrometers, and on-chip digitization merge sensing, storage, and computing into a single chip. The integration enables monolithic infrared systems with more compact architectures while possessing adaptive perception, data compression, and real-time signal processing capabilities. Finally, a comparative analysis containing material engineering, microstructure design, and integrated architecture is presented to outline the challenges and opportunities toward compact, intelligent, multifunctional infrared detection platforms.

Quantum well (QW)-enhanced plasmonic substrates have been demonstrated to improve the blinking fluorescence of spontaneously blinking fluorophores, which enhances the localization precision and density for single-molecule localization microscopy (SMLM). The QW-enhanced plasmonic substrate consists of a three-repeat InGaN QW structure covered by Al nanoparticles. In addition to the localized surface plasmon enhancement produced by Al nanoparticles, InGaN QWs with tunable discrete energy levels and a high-density surface charge distribution can facilitate additional charge transfer resonances. This effect further enhances the local surface plasmon resonance around the Al nanoparticles. Moreover, the interaction between the high-density surface charges of the InGaN QWs and the oscillating electrons of the Al nanoparticles can lead to another type of surface plasmon enhancement effect. Therefore, the blinking intensity and event frequency are significantly increased, resulting in improved SMLM image resolution under the wide-field fluorescence excitation. With multiple fluorescence enhancement effects, the QW-enhanced plasmonic substrate enables SMLM imaging of phosphorylated epidermal growth factor receptors (EGFRs) in A549 lung cancer cells to quantitatively investigate the inhibition of EGFR tyrosine kinase. Furthermore, this QW-enhanced plasmonic substrate can reduce the excitation power needed for SMLM imaging at an acceptable resolution.

With respect to a III-nitride monolithic photonic circuit comprising multiple quantum well (MQW) diodes, InGaN/GaN MQW transmitters/boosters convert pulse optical signals into emitted light, whereas MQW modulators/receivers/monitors transform modulated shorter-wavelength photons into electronic signals. Here, five MQW diodes are interconnected via optical waveguides on a single III-nitride monolithic photonic chip, with an operating wavelength range of 385–416 nm. By integrating functional circuits with a time-division multiplexing (TDM) scheme, the light-emitting and light-detecting functionalities of these MQW diodes can be dynamically redefined, enabling a reconfigurable optical communication architecture. Each equipotential and fully mapped node serves as a core technology for scalable on-chip optical networks, allowing the reconfigurable III-nitride photonic chip and TDM scheme to integrate additional MQW components seamlessly.

We theoretically investigate how the injector region design of interband cascade lasers (ICLs) impacts the threshold carrier and current densities. The model combines a polarization-sensitive 8-band k⋅p calculation, electrostatics, and a microscopic calculation of Auger recombination rates. The inelastic carrier–carrier scattering is included at the lowest order using quasi-equilibrium Green’s functions. Our approach captures the combined effects of charge-carrier redistribution, parasitic absorption, and bias voltage on the Auger recombination rate. We show that heavily doping the electron injector suppresses the dominant multi-hole Auger recombination by reducing the hole population of the recombination quantum wells. This agrees with the experimental observation that the heavy doping reduces threshold currents. Unlike the measurements, however, they do not increase at high doping concentrations in our model, which does not include scattering-mediated carrier escape and/or light absorption. Furthermore, by introducing indium to the conventional GaSb hole injector wells, we explain the rule of thumb from experiments that raising the hole injector levels does not outperform the doping strategy. Our model provides physical insights for optimizing ICL carrier injectors.

Abstract In this paper, we have designed and analyzed a room temperature near-infrared quantum cascade laser with wavelength of λ=1.05 μm from Si/CaF2 heterojunction and distributed feedback (DFB) conduction layer. The designed device contains multi-Si/CaF2 active layer on n-Si (111) layer of a silicon-on-insulator (SOI) substrate, forming a single-mode propagation waveguide in transverse magnetic (TM) mode. We innovatively designed the active layer structure that consists of a 12-monolayer (ML) transition layer quantum well (QW), quad-injector-barrier and a 4-ML blocking layer, with transition from 4th state to 1st state in QW. The minimum threshold current density of 7.32 kA/cm2 was obtained at waveguide width of 0.25 μm, period number of 15, and conduction layer (CL) thickness of 25 nm, which is lower than calculated injection current density of 31 kA/cm2.

Quantum well infrared photodetectors (QWIPs) have emerged as a high-performance and versatile platform for IR detection applications owing to their design flexibility, fast response time, and wavelength tunability across a wide spectral range. While research and development in this field have predominantly focused on GaAs-based QWIPs owing to their mature growth technique and well-understood material properties, III-nitride-based QWIPs can offer potential advantages such as a wider bandgap and strong polarization charges. However, the study of GaN-based QWIPs is still in its early stages and requires further exploration to achieve optimal device performance. Compared to n-QWIPs, p-QWIPs allow for normal-incident absorption, significantly reducing device complexity and size by eliminating the light coupler, which is particularly advantageous for hand-held and imaging applications. We perform detailed atomic-scale characterization of the distribution of Mg acceptors in layers and at interfaces of a Mg-doped AlGaN/GaN p-QWIP grown by metal organic chemical vapor deposition. Device design, device structure growth conditions, and electrical characterization of the QWIP are presented. Initial electrical characterizations revealed a small but noticeable increase in photocurrent upon illumination. We suspect that photoresponsivity (∼μA/W) is highly impacted by low or inefficient Mg incorporation in the QWIP, limiting the carrier population in quantum wells. Atom probe tomography was employed to study the Mg concentration and distribution in the Mg-doped AlGaN/GaN p-QWIP and revealed Mg segregation and clustering in QWIP layers. These findings provide critical insights and pathways to enhance photoresponsivity and overall device performance in QW-based devices that require Mg p-doping.

Integration of III-V membranes on silicon-on-insulator (SOI) substrates offers a promising route to provide on-chip gain for dense silicon (Si) photonics. Here, we present a materials study of InP membranes with embedded InGaAs multi-quantum wells (MQWs) directly grown above the Si waveguide layer via a tunnel epitaxy process. Cross-sectional scanning transmission electron microscopy, combining differential phase contrast imaging, energy-dispersive x-ray spectroscopy (EDX), and atomic-column-based strain analysis, confirms high-quality laterally grown InP membranes with defects confined to the V-groove region and elucidates facet-dependent MQW formation on (111)A, (110), and (111)B facets. Both EDX and strain analysis consistently reveal high-In, highly compressively strained (110) QWs (>80% In), and no misfit dislocations are observed at InP/InGaAs interfaces. In addition, under identical precursor ratios, ultra-thin QWs incorporate a higher indium composition than a thick bulk InGaAs region. These results provide practical guidance for designing efficient active regions in future electrically injected, Si-waveguide-coupled InP membrane lasers on SOI.

N-polar GaN high-electron-mobility transistors (HEMTs) show unique transfer characteristics originating from the band structure related to the inverted HEMTs, and some scattering mechanisms are suggested theoretically. However, their experimental verification has not been sufficiently discussed yet. In this paper, we compared the experimentally obtained field-effect mobilities of N-polar and Ga-polar GaN HEMTs with each calculated scattering component using the self-consistent 1-dimensional Poisson–Schrödinger calculation, revealing the origin of the differences as the distance between the 2DEG centroid and the GaN/AlN or AlN/GaN interface. Mobility of Ga-polar GaN HEMT was superior to N-polar HEMT despite 2.5 times higher scattering center density, and the highly narrowed quantum well of N-polar GaN HEMT was the dominant factor.

Structural and field-induced control of optical properties in a novel exponentially bounded cosine quantum well

Incorporation of ZnSnN₂ and InN δ-layers in InGaN/GaN Quantum Wells: Toward efficient long-wavelength III-nitride LEDs

Theoretical Investigation of Optical Properties in GaAs Quantum Wells under Position-Dependent Mass and Semi-Confined Effects

InGaN photonic devices with the integrated multiple-quantum-well (MQW) light-emitting diode (LED), photodiode (PD) and ridge waveguide for chip-level data connectivity

We demonstrate a high-power InGaAs/GaAs quantum well (QW) gain chip that achieves a suppressed linewidth enhancement factor (α-factor) by utilizing the second conduction subband (E2) transition. The low α-factor is intrinsically enabled by operating the device on the E2 transition, while high-power single-mode operation is ensured by an asymmetric epitaxial waveguide and a J-shaped ridge structure. The device exhibits a gain peak shift from 1050 nm (first conduction subband (E1) transition) to 990 nm (E2 transition) at high current injection, achieving a fundamental transverse-mode output of 180.01 mW, with α-factor suppressed. Compared to the E1 transition, the E2 transition offers a sixfold reduction in α-factor and demonstrates markedly lower sensitivity to carrier fluctuations. Additionally, the E2 transition yields a higher gain than E1, enhancing the potential for high-power scaling. This work validates E2-transition engineering as an effective strategy for high-performance narrow-linewidth light sources.

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.

Abstract Bulk InGaN with approximately 20% indium (In) content demonstrates efficient red emission facilitated by strain relaxation-induced phase separation, which challenges traditional multiple quantum well structures. Through various transmission electron microscopy (TEM) techniques, we revealed that strain relaxation induces the spontaneous formation of lamellar, high-In-content clusters along the trench sidewalls. Hyperspectral cathodoluminescence in TEM system directly links these phase-separated domains to red emission. Processed into micro-light-emitting diodes (Micro-LEDs), the bulk InGaN exhibits remarkable luminescent performance, including minimal efficiency droop and only a 4 nm blue shift over a current density range of 5–100 A cm −2 . This work establishes phase separation as a controllable mechanism for bandgap engineering in relaxed III-nitride systems, with significant potential for InGaN-based red Micro-LED applications.

Quantum wells made of quasi two-dimensional organic-inorganic hybrid perovskites (2D-PKs) offer a high degree of flexibility in tailoring optoelectronic properties through carrier confinement and functional interlayers. Compared to their 3D counterparts, 2D-PKs exhibit tunable photoluminescence, excitonic binding at room temperature, and enhanced structural stability. However, the dynamics of photoinduced charge carriers and their transport properties are highly intertwined due to the interplay of diverse excitation species, charge carrier cooling, transport, and radiative and non-radiative recombination. In this study, we employ optical-pump terahertz-probe spectroscopy (OPTP) to analyze the local conductivity dynamics of 2D-PK (n = 5) 2-(9H-carbazol-9-yl)ethan-1-ammonium [(MA)5(CzEA)2(PbI3)5] and 3D-MAPI methylammonium lead iodide (MeNH3PbI3) perovskites on picosecond timescales. Remarkably, we observe an intensity-dependent, 2D-specific buildup of an ultrafast, few-picosecond decay in local THz-conductivity. By combining OPTP with transient absorption and picosecond time-resolved photoluminescence (tr-PL), we correlate photoconductivity and carrier population. Thus, we can attribute the 2D-specific ultrafast THz response to delayed hot-carrier cooling and subsequent exciton formation, which effectively reduces the free-carrier conductivity. This intensity-dependent, ultrafast THz response appears as a signature of the recently identified hot-carrier bottleneck in bulk perovskites, and this effect manifests itself in a unique form in the 2D material. These results encourage further investigations on the impact of functional organic interlayers and provide insights into designing tunable carrier responses for ultrafast devices via adapted heterostructures and confinements.

Metasurface-integrated semipolar (2021) ¯ In𝑥Ga₁−𝑥N quantum wells towards efficient circularly-polarized LEDs

We have systematically investigated current density–bias voltage ( J – V b ) characteristics of GaAs/Al 0. 4 Ga 0. 6 As superlattices (SLs) with almost the same miniband width but with different quantum well thicknesses, L w . Despite similar miniband width, small changes in L w led to a marked variation in J – V b characteristics. By fitting the data with an extended Esaki–Tsu model that includes energy and momentum relaxation processes, we find that the momentum relaxation time depends strongly on L w as L w 3–5 , probably due to increased interface roughness scattering in narrower quantum wells. Our results highlight crucial roles of L w and interface quality in optimizing electron transport in SLs.