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With the advancement of perovskite research, there is a growing urgency to address the imperative need for practical applications while simultaneously tackling the enduring challenges of material reliability and lead (Pb) toxicity. The crystallization, morphology and optical properties of the resultant film and device performance during solution processing are heavily influenced by the solution-based intermediate, a state determined using the coordination between solute and solvent. Solvent–solute coordination is closely correlated with solvent characteristics including ionization capabilities, dielectric constant, hydrolysis, and reactivity with solutes. Deionized water (D-water) characterized by its high polarity, ionization capability, and dielectric constant, when used as a co-solvent with dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), facilitates stronger coordination with CsI/SnI4 species in Cs2SnI6 precursor solution. This enhanced coordination leads to improved solvation, precursor reactivity, and solution homogeneity. Incorporating an appropriate amount of D-water as a co-solvent into Cs2SnI6 precursor solution allows for tuning solvent coordination and control over the resulting thin film crystallization and morphology. The co-solvent diluted optimized Cs2SnI6 thin film leads to the fabrication of energy-efficient broadband 4 × 3 photodetector arrays ranging from UV to NIR giving a responsivity of 5.5 A W−1 at a substantially lower bias voltage of −0.1 V with stable operation stability in ambient air. These findings underscore the potential advantages of solution-processed Cs2SnI6 perovskites in various optoelectronic applications. [ABSTRACT FROM AUTHOR]

Density functional theory computations were utilized to quantify the polarization discontinuity of 1.8 μC/cm2 in ε-(B0.0625Ga0.9375)2O3/ε-Ga2O3 heterostructure. The polarization effect was sufficient to generate a two-dimensional electron gas (2DEG) at the heterostructure interface without doping. The creation of 2DEG occurred when the BGaO layer thickness exceeded 17 nm, with its density exhibiting a logarithmic increase as the thickness was augmented. However, the trend plateaued when the thickness surpassed 80 nm with a carrier density of 8.17 × 1012 cm–2. Moreover, guided by Griffith's theory and enthalpy calculations, the epitaxial layer could potentially be pseudomorphically grown up to 968 nm under growth conditions of 1000 K with dilute boron alloying. This design heralds the potential for creating a high electron mobility transistor based on ε-BGaO with an epitaxial layer just nanometers thick, well-suited for high-power and radio frequency applications. [ABSTRACT FROM AUTHOR]

Polarization-sensitive photodetection and imaging have great application value in fields such as polarization division multiplexing optical communication, remote sensing, near-field imaging and military monitoring. Pursuing a high polarization ratio has always been the research hotspot in polarization-sensitive photodetectors. In this paper, we report a compression strain enhanced polarization ratio in β-gallium oxide (β-Ga2O3) single crystal flake. A rigorous crystallographic analysis confirmed its high crystalline quality and orientation. Angle-resolved polarization Raman spectroscopy (ARPRS) was adopted to study the anisotropy of its optical properties. Extensive ARPRS measurements and theoretical calculation consistently demonstrate the strong optical anisotropy in the high-quality β-Ga2O3 flake. A polarization ratio of 0.96 was obtained in the flat β-Ga2O3 flake. Furthermore, mechanical strain of ±0.7% was introduced into β-Ga2O3. An increased polarization ratio of 0.98 was achieved in the case of 0.7% compression strain, which is, to the best of our knowledge, the highest value for UVC polarization-sensitive photodetectors. That corresponds to an improved polarization rejection ratio of 100. This work proposed a new path towards improving polarization sensitivity by applying strain engineering in the active material. [ABSTRACT FROM AUTHOR]

Spectroscopic identification of defects and impurities is crucial for understanding doping asymmetry issues in ZnO and, therefore, realization of true ZnO-based bipolar devices. Chlorine (Cl) is an amphoteric impurity in ZnO exhibiting acceptor behavior in the interstitial configuration and donor action once on substitutional oxygen sites (ClO). In its turn, the incorporation of Cl atoms depends on the material growth conditions and a ClO fraction should be suppressed in O-rich materials. In the present work, Cl ions were implanted into ZnO thin films synthesized under O-rich conditions. In contrast to a negligible effect of Cl incorporation to electrical conductivity, photoluminescence measurements revealed dramatic developments of optical properties with a strong acceptor-like spectral signature emerging after 900 °C anneals. We discuss the origins of a new excitonic I* line (3.355 eV) induced by Cl-implantation and propose two alternative defect models based on shallow acceptor and shallow donor complexes. [ABSTRACT FROM AUTHOR]

Controlling the formation of interstitial Na (Nai) self-compensating defects has been a long-term physics problem for effective Na doping in ZnO. Herein, we present an experimental approach to the suppression of Nai defects in ZnO via Na and F codoping under an oxygen-rich condition during the molecular beam epitaxy growth process. It is found that the incorporation of such large numbers of Na and F dopants (∼1020 cm−3) does not cause an obvious influence on the lattice parameters. Hall-effect measurements demonstrate that F doping efficiently raises the Fermi level (EF) of ZnO films, which is expected to make the formation energy of Nai and NaZn increase and decrease, respectively. Most of the Na atoms occupy the substitutional Zn sites, and the formation of Nai is suppressed consequently. Secondary ion mass spectrometry measurements reveal that F and Na atoms are tightly bonded together due to their strong Coulomb interaction. The enhanced deep level emission (DLE) in ZnO:Na-F is ascribed to the considerable amount of isolated Zn vacancy (VZn) defects induced by the elevated EF and the formation of neutral F O + − N a Zn − 0 complexes. On the other hand, formation of F O + − V Zn 2 − − complexes in ZnO:F exhausts most of the isolated Zn vacancies, leading to the disappearance of the DLE band. [ABSTRACT FROM AUTHOR]

Owing to the intrinsically wide bandgap and high uniformity, amorphous Ga2O3 (a-Ga2O3) has been illustrating a great industrial potential for large-area deep ultraviolet (UV) photosensor arrays. However, a seemingly irreconcilable contradiction between high responsivity and long persistent photoconductivity has hampered the growing pace of such devices. In this work, three-terminal InGaZnO (IGZO)/a-Ga2O3 dual-active-layer (DAL) transistors were developed to realize the ability of a-Ga2O3 as the active layer both in switching and sensing. Benefitting from the introduction of ultrathin IGZO electron reservoir and defect control of a-Ga2O3, the DAL device demonstrates more stable and superior gate-control capability with promising performance including high on/off ratio and field-effect mobility of ∼108 and 8.3 cm2/V⋅s, respectively, as well as a small sub-threshold swing (SS) of 0.36 V/dec. Under 254 nm UV illumination, the DAL device manifests a light-to-dark ratio of ∼108, a responsivity of 4.8 × 103 A W−1, a detectivity of 8 × 1015 Jones, and a UV/visible rejection ratio (R254/R400) of 64. The simultaneous achievement of deep UV photo-detection and transistor's switching performance in a-Ga2O3 material offers excellent potential for the construction of large-area active-matrix UV photosensor arrays with the simple and low-cost fabrication process. [ABSTRACT FROM AUTHOR]

Developing optoelectronic synaptic devices with low energy consumption is of critical importance for neuromorphic computing and visualization systems. In this work, amorphous‐Ga2O3 (a‐Ga2O3) is adopted to realize a low‐power optoelectronic synapse considering its distinguished features of ultra‐wide bandgap, high responsiveness to light stimulation, and strong persistent photoconductivity effect. The basic synaptic functions such as short‐term plasticity (STP) and long‐term plasticity (LTP) have been successfully mimicked. A noise suppression capability is achieved as well, similar to the visual cells. Strikingly, the total energy consumption for triggering an LTP synaptic event is only 136 fJ, approaching the one of a biological synapse. The underlying mechanism for the a‐Ga2O3 synaptic performance is explored with a combined research of X‐ray photoelectron spectroscopy, Kelvin probe force microscopy, electric tests, and Technology Computer‐Aided Design simulations. The consistent results suggest the key role of the synergetic modulation effect of optical and electric fields on the dynamic behaviors of oxygen vacancy (VO) defects. This work indicates the potential applications of a‐Ga2O3 in low‐power optoelectronic synapses. [ABSTRACT FROM AUTHOR]