Interfacial disorders in semiconductor quantum wells (QWs) determine material properties and device performance and have attracted great research efforts using different experimental methods. However, so far, there has been no way to quantify the lateral length distribution of the interfacial disorders in QWs. Since photoluminescence (PL) is sensitive to exciton localization, the evolutions of PL energy and linewidth under external perpendicular magnetic fields have served as effective measurement methods for QW analysis; however, the evolution of PL intensity has not played a matching role. In this paper, we develop a theoretical model correlating the PL intensity with the interfacial disorders of type-I QWs under an external perpendicular magnetic field. We verify the model's rationality and functionality using InGa(N)As/GaAs single QWs. In addition, we derive the Urbach energy and determine the lateral length distribution of interfacial disorders. The results show that the magnetic field-dependent PL intensity, as described by our model, serves as a valid probe for quantifying the interface flatness. The model also reveals that the mechanism of magnetic-field-induced intensity enhancement is a joint effect of interfacial disorder-induced exciton localization and the transfer of excitons from dark to bright states. These insights may benefit performance improvements of type-I QW materials and devices.

Cesium lead bromide perovskites have demonstrated enormous potential in detecting applications, benefitting from their excellent optoelectronic properties and environmental stability. However, their intrinsic properties of photoluminescence intensity and carrier lifetime, key to photodetector performance, are still limited with conventional approaches (e.g., material purification and defect passivation). Here, we propose an efficient ultrasound-assisted growth method to manipulate the crystal phase of all-inorganic perovskites. Morphological, structural, and elemental characteristics of perovskites are comprehensively investigated, confirming the formation of CsPb2Br5–CsPbBr3 dual-phase (DP) perovskites. The fabricated DP perovskites exhibit enhanced carrier dynamics compared to CsPbBr3 quantum dots (QDs), including over a tenfold increase in photoluminescence intensity and an extended carrier lifetime of 656 ns. Such impressive improvements originate from the repeated radiative recombination introduced by the hierarchical phase of DP perovskites. As a result, the DP perovskite-based photodetector also demonstrates improved photoresponse, including a larger on/off ratio exceeding 103 and a higher detectivity of 1.48 × 1010 Jones, especially in the absence of conventional transporting layers. These results offer strong competitiveness for state-of-the-art perovskite photodetectors and deliver important implications for the widespread use of DP perovskites in assembling high-performance optoelectronic devices.

Due to high responsivity and wide spectral sensitivity, metal halide perovskite photodiodes have a wide range of applications in the fields of visible light and near-infrared photodetection. Specific detectivity is an important quality factor for high-performance perovskite-based photodiodes, while one of the keys to achieving high detectivity is to reduce dark current. Here, 3-fluoro phenethylammonium iodide (3F-PEAI) was used to passivate the perovskite surface and form the two-dimensional (2D) perovskite on the three-dimensional (3D) perovskite surface. The as-fabricated passivated perovskite photodiodes with 2D/3D hybrid-dimensional perovskite heterojunctions showed two orders of magnitude smaller dark current, larger open circuit voltage and faster photoresponse, when compared to the control perovskite photodiodes. Meanwhile, it maintained almost identical photocurrent, achieving a high specific detectivity up to 2.4 × 1012 Jones and over the visible-near-infrared broadband photodetection. Notably, the champion photoresponsivity value of 0.45 A W−1 was achieved at 760 nm. It was verified that the 2D capping layers were able to suppress trap states and accelerate photocarrier collection. This work demonstrates strategic passivation of surface iodine vacancies, offering a promising pathway for developing ultrasensitive and low-power consumption photodetectors based on metal halide perovskites.

Interfacial disorder in semiconductor quantum well (QW) determines material properties and device performance, and has drawn great research efforts using different experimental methods, yet there was not a method quantifying the lateral-length distribution of the interfacial disorders in QWs. Photoluminescence (PL) is sensitive to exciton localization, the evolutions of PL energy and linewidth with external perpendicular magnetic field have served as effective quantities for QW analysis, yet the evolution of PL intensity did not play a matchable role. We in this work develop a theoretical model correlating the PL intensity with the interfacial disorders of type-I QWs in an external perpendicular magnetic field, verify its rationality and functionality with InGa(N)As/GaAs single QWs, and derive Urbach energy and lateral-length distribution of interfacial disorders. The results show that the model makes the magnetic field-dependent PL intensity a valid probe for quantifying the interface flatness, reveals the mechanism of magnetic field-induced intensity enhancement as a joint effect of interfacial disorder-induced exciton localization and transfer of excitons from dark to bright states, and may benefit performance improvement of type-I QW materials and devices.

The effect of Bi on the emission temperature sensitivity of GaAsBi remains a topic of debate, which hinders the design of optoelectronic devices. Band‐tail states, which are critical for GaAsBi performance, are suspected to drive the discrepancy, but their effect remains unclear. This work resolves the key debate using an innovative dual‐spectroscopy approach that combines temperature‐dependent photoluminescence (PL) and transmission spectroscopy to decouple the contributions of band‐tail states from intrinsic band‐edge behavior. For GaAs 1‐ x Bi x ( x = 0.033, 0.048), the energy‐temperature coefficients derived from transmission are composition‐independent, while those derived from PL decrease by ≈40% with higher Bi content. This apparent contradiction originates from the thermalized carrier redistribution between the valence band and band‐tail states at elevated temperatures and the intrinsic band‐edge thermal sensitivity in the transmission spectra. The dual‐spectroscopy approach is proven to be an effective method for clarifying the effects of band‐tail states on the thermal sensitivity, and provides valuable guidance for the design of stable GaAsBi optoelectronic devices.

The imaging performance of infrared focal plane array (FPA) is limited by the non-uniformity of the in-plane response of InAs/GaSb type II superlattices (T2SL) consisting of a few hundred or more thin layers. Fundamentally, the non-uniformity results from the materials' property variation and process fluctuations over an area of a square centimeter. Thus, the influence of materials and processes on the uniformity of internal response is necessary to accurately detect and evaluate to improve the imaging performance of an FPA detector. In this work, spatially resolved photoluminescence (PL) was implemented to detect the microscale mesa pixels, and the effects of materials and processes on spatial uniformity were studied for the first time. Modulated PL-mapping technology based on step-scan Fourier transform infrared spectrometry was used to extract parameters from each test spectrum, such as PL peak energy, linewidth, and integral intensity, which were then analyzed by 2D spatial mapping. Results showed that the variation of T2SL material properties accounted for 29% of the non-uniformity, and the remaining 71% resulted from the process fluctuation. In particular, the etching process had a great influence on the uniformity. The non-uniformity of the integral intensity of the sample after etching increased by 2.44 times compared with that before etching. Thereafter, a layer of SiO2 film was deposited to passivate the surface. The results showed that the non-uniformity returned to the level before etching, which directly proves that the passivation process can improve the response uniformity of the infrared FPA detector.

Herein, low‐temperature and temperature‐dependent photoluminescence (PL) measurements are carried out on highly tensile‐strained Ge nanostructures embedded in GaSb matrix, and the effects of Ge deposition thickness are clarified. The direct‐gap transition‐related PL feature is successfully identified in the tensile‐strained Ge nanostructures. While typical PL thermal quenching is observed for the tensile‐strained Ge‐ and GaSb‐related transitions in the samples with a Ge deposition being thinner than the critical thickness, a negative thermal quenching shows up for the GaSb interband transition in the samples with Ge deposition surpassing the critical thickness at which high‐density nanoparticles form to relax the strain. A phenomenological thermal‐injection model is established of electrons from the tensile‐strained Ge layer to the GaSb matrix, the thermal quenching is accounted for, and a ladder‐like function of the strain‐relaxed Ge is clarified to favor the electron activation. The understanding of the effects of deposition thickness is helpful for the high‐performance Ge‐based light source for optoelectronic integration.

The properties of InAs/In0.53Ga0.37As triangular quantum wells (QWs) grown on an InP/SiO2/Si integrated substrate by ion-slicing technology are investigated. The material structure and growth quality are characterized by the X-ray diffraction (XRD) and transmission electron microscope measurements. The photoluminescence (PL) spectra at various temperatures are also analyzed. The PL peak wavelengths red-shift from 1.94 to 2.13 mu m with the increase of temperature from 12.4 to 300 K. The experimental results of the QWs on InP/SiO2/Si substrate are found to be comparable with the performance of the same QWs grown on an InP substrate. The results are promising for future integration of Si with InP-based optical devices for the applications of light emission in mid infrared wavelength range.

InAs/In0. 83Al0. 17As quantum wells have been demonstrated on In0. 83Al0. 17As metamorphic layers on GaP/Si substrates. The effects of GaxIn1-xP and GaAsyP1-y graded buffer layers on the sample performances are investi?gated. The sample with GaxIn1-xP metamorphic buffer layer has narrower width in X-ray diffraction reciprocal space maps,indicating less misfit dislocations in the sample. Mid-infrared photoluminescence signals have been observed for both samples at room temperature,while the sample with GaxIn1-xP metamorphic buffer shows stron?ger photoluminescence intensity at all temperatures. The results indicate the metamorphic buffers with mixed cat?ions show superior effects for the mid-infrared InAs quantum wells on GaP/Si composite substrates.

We characterize the opto-mechanical properties of double-layer mechanical devices. These closely spaced photonic crystal membranes can exhibit photonic bound states in the continuum, which could enable the realization of a strongly coupled, integrated op-tomechanical system.

The sensitive parameters affecting the dark current characteristics are further studied by using InAs/GaSb type II superlattice (T2SL) pBpp structure long wavelength Infrared photodetectors.Generation of recombination (G-R), surface leakage current and tunneling current are the main components of dark current. Using pBpp structure can suppress them effectively, thereby decreasing dark current. Based on the k ∙ p method, the band structure of InAs/GaSb T2SL and InAs/AlSb T2SL can be obtained by solving the 8-band k ∙ p model. We have calculated different doping levels of pBpp detector and different layer thicknesses of pBpp detector. For pBpp device, we consider the dark current for different contact layer doping and different absorber layer doping. We also study the influence of different contact layer thicknesses and different absorber layer thicknesses on dark current. The dark current of pBpp detector is dominant by tunneling current at low temperature, and diffusion is the main limiting mechanism in dark current at high temperature, for barrier layer inhibits generation-recombination contribution. Eventually, the dark current of a pBpp structure has been calculated for versus voltage at 77 K.

In-plane uniformity of narrow-gap semiconductor InAs/GaSb type-II superlattice (T2SL) wafer is a crucial yet hard-to-evaluate prerequisite for high-performance long-wavelength infrared optoelectronic device applications of, e.g., focal-plane-array (FPA) photodetectors. In this work, we report a modulated photoluminescence-mapping (PL-mapping) study of InAs/GaSb T2SL in long-wavelength infrared range with a spatial resolution of a typical FPA-pixel scale. Spatial distributions are analyzed of PL-peak energy, linewidth, and integral intensity, which indicate a high in-plane uniformity of effective band gap but a considerable fluctuation of radiative recombination. The in-plane distributions of effective carrier lifetime and Shockley-Read-Hall defect concentration are evaluated, with the aid of a model that takes into account the pumping power dependence of the PL integral intensity. The results reveal a considerable in-plane nonuniformity of the optoelectronic response that may restrict the performance of the derivative FPA photodetector, and indicate the modulated PL mapping of a good pathway particularly for uniformity analysis of long-wavelength infrared FPA semiconductors.

Three-inch InGaAs epilayers are grown by solid source molecular beam epitaxy using the manipulator equipped with dual-zone heaters. The effects of the substrate temperature on the uniformity of material surface morphology, indium composition, photoluminescence, electronic mobility, and background doping are investigated. As the temperature of the outer heater in the range of 625 degrees C to 655 degrees C, no dim area is observed on the edge of the material surface. At the same time, the indium composition fluctuation of the high-resolution X-ray diffraction and the photoluminescence wavelength fluctuation are less than +/- 0.1% for the epilayers grown at the optimum substrate temperatures.

We fabricated and characterized suspended bi-layered photonic crystal slabs in AlGaAs heterostructures. Our approach allows to create integrated, closely spaced membranes, which can exhibit photonic bound states in the continuum to increase light-matter interaction.

We present high-reflectivity mechanical resonators fabricated from AlGaAs heterostructures for use in free-space optical cavities operating in the telecom wavelength regime. The mechanical resonators are fabricated in slabs of GaAs and patterned with a photonic crystal to increase their out-of-plane reflectivity. Characterization of the mechanical modes reveals residual tensile stress in the GaAs device layer. This stress results in higher mechanical frequencies than in unstressed GaAs and can be used for strain engineering of mechanical dissipation. Simultaneously, we find that the finite waist of the incident optical beam leads to a dip in the reflectance spectrum. This feature originates from coupling to a guided resonance of the photonic crystal, an effect that must be taken into account when designing slabs of finite size. The single-layer and sub-μm-spaced double-layer slabs demonstrated here can be directly fabricated on top of a distributed Bragg reflector mirror in the same material platform. Such a platform opens a route for realizing integrated multi-element cavity optomechanical devices and optomechanical microcavities on chip.

Strain and stress were simulated using finite element method (FEM) for three III–V-on-Insulator (III–VOI) structures, i.e. , InP/SiO 2 /Si, InP/Al 2 O 3 /SiO 2 /Si, and GaAs/Al 2 O 3 /SiO 2 /Si, fabricated by ion-slicing as the substrates for optoelectronic devices on Si. The thermal strain/stress imposes no risk for optoelectronic structures grown on InPOI at a normal growth temperature using molecular beam epitaxy. Structures grown on GaAsOI are more dangerous than those on InPOI due to a limited critical thickness. The intermedia Al 2 O 3 layer was intended to increase the adherence while it brings in the largest risk. The simulated results reveal thermal stress on Al 2 O 3 over 1 GPa, which is much higher than its critical stress for interfacial fracture. InPOI without an Al 2 O 3 layer is more suitable as the substrate for optoelectronic integration on Si.

Heterogeneous integration of compound semiconductors on a Si platform leads to advanced device applications in the field of Si photonics and high frequency electronics. However, the unavoidable bubbles formed at the bonding interface are detrimental for achieving a high yield of dissimilar semiconductor integration by the direct wafer bonding technology. In this work, lateral outgassing surface trenches (LOTs) are introduced to efficiently inhibit the bubbles. It is found that the chemical reactions in InP–Si bonding are similar to those in Si–Si bonding, and the generated gas can escape via the LOTs. The outgassing efficiency is dominated by LOTs’ spacing, and moreover, the relationship between bubble formation and the LOT’s structure is well described by a thermodynamic model. With the method explored in this work, a 2-in. bubble-free crystalline InP thin film integrated on the Si substrate with LOTs is obtained by the ion-slicing and wafer bonding technology. The quantum well active region grown on this Si-based InP film shows a superior photoemission efficiency, and it is found to be 65% as compared to its bulk counterpart.

The structural properties of GeSn thin films with different Sn concentrations and thicknesses grown on Ge (001) by molecular beam epitaxy (MBE) and on Ge-buffered Si (001) wafers by chemical vapor deposition (CVD) were analyzed through high resolution X-ray diffraction and cross-sectional transmission electron microscopy. Two-dimensional reciprocal space maps around the asymmetric (224) reflection were collected by X-ray diffraction for both the whole structures and the GeSn epilayers. The broadenings of the features of the GeSn epilayers with different relaxations in the ω direction, along the ω-2θ direction and parallel to the surface were investigated. The dislocations were identified by transmission electron microscopy. Threading dislocations were found in MBE grown GeSn layers, but not in the CVD grown ones. The point defects and dislocations were two possible reasons for the poor optical properties in the GeSn alloys grown by MBE.

The effect of an external electric field on the exciton states of InGaAsP/InP core–shell quantum dots is investigated through the variational method. The effect of the shell thickness, core radius, electric field strength, and material components on the exciton states are analyzed in detail. The numerical results show that the electron and hole energies decrease as the shell thickness or core radius is increased. The Bohr radius is a nonmonotonic function of the shell thickness or core radius, and the change of the exciton binding energy is nonlinear as the shell thickness or core radius is increased. With increasing electric field strength, the Bohr radius increases while the exciton binding energy decreases. The exciton binding energy decreases (increases) as the Ga (As) component is increased.

Dilute bismide and nitride provide flexible bandgap and strain engineering, owing to their unique physical properties, and are attractive for mid-IR (2–12 μm) optoelectronic device applications. In this chapter, we review progresses of theoretical simulations, epitaxial growth, material characterizations, and devices of dilute bismides including GaSbBi, AlSbBi, InAsBi, InAsSbBi, InGaAsBi, and InSbBi, as well as dilute nitrides including InNAs, GaNSb, InNSb, GaInNAs, and InNAsSb. The overview mainly focuses on growth optimization, optical characterizations, and theoretical calculations ending with outlook remarks about advantages and main challenges of both exotic materials.