GaN has been widely used in the fabrication of ultraviolet photodetectors because of its outstanding properties. In this paper, we report a graphene–GaN nanorod heterostructure photodetector with fast photoresponse in the UV range. GaN nanorods were fabricated by a combination mode of dry etching and wet etching. Furthermore, a graphene–GaN nanorod heterostructure ultraviolet detector was fabricated and its photoelectric properties were measured. The device exhibits a fast photoresponse in the UV range. The rising time and falling time of the transient response were 13 and 8 ms, respectively. A high photovoltaic responsivity up to 13.9 A/W and external quantum efficiency up to 479% were realized at the UV range. The specific detectivity D^* = 1.44 × 10¹⁰ Jones was obtained at –1 V bias in ambient conditions. The spectral response was measured and the highest response was observed at the 360 nm band.

In this work, the optimization of reverse leakage current (I_R) and turn-on voltage (V_T) in recess-free AlGaN/GaN Schottky barrier diodes (SBDs) was achieved by substituting the Ni/Au anode with TiN anode. To explain this phenomenon, the current transport mechanism was investigated by temperature-dependent current–voltage (I–V) characteristics. For forward bias, the current is dominated by the thermionic emission (TE) mechanisms for both devices. Besides, the presence of inhomogeneity of the Schottky barrier height (qφ_b) is proved by the linear relationship between qφ_b and ideality factor. For reverse bias, the current is dominated by two different mechanisms at high temperature and low temperature, respectively. At high temperatures, the Poole–Frenkel emission (PFE) induced by nitrogen-vacancy (V_N) is responsible for the high I_R in Ni/Au anode. For TiN anode, the I_R is dominated by the PFE from threading dislocation (TD), which can be attributed to the decrease of V_N due to the suppression of N diffusion at the interface of Schottky contact. At low temperatures, the I_R of both diodes is dominated by Fowler–Nordheim (FN) tunneling. However, the V_N donor enhances the electric field in the barrier layer, thus causing a higher I_R in Ni/Au anode than TiN anode, as confirmed by the modified FN model.

In this article, we present a theoretical study on the sub-bandgap refractive indexes and optical properties of Si-doped β-Ga₂O₃ thin films based on newly developed models. The measured sub-bandgap refractive indexes of β-Ga₂O₃ thin film are explained well with the new model, leading to the determination of an explicit analytical dispersion of refractive indexes for photon energy below an effective optical bandgap energy of 4.952 eV for the β-Ga₂O₃ thin film. Then, the oscillatory structures in long wavelength regions in experimental transmission spectra of Si-doped β-Ga₂O₃ thin films with different Si doping concentrations are quantitively interpreted utilizing the determined sub-bandgap refractive index dispersion. Meanwhile, effective optical bandgap values of Si-doped β-Ga₂O₃ thin films are further determined and are found to decrease with increasing the Si doping concentration as expectedly. In addition, the sub-bandgap absorption coefficients of Si-doped β-Ga₂O₃ thin film are calculated under the frame of the Franz–Keldysh mechanism due to the electric field effect of ionized Si impurities. The theoretical absorption coefficients agree with the available experimental data. These key parameters obtained in the present study may enrich the present understanding of the sub-bandgap refractive indexes and optical properties of impurity-doped β-Ga₂O₃ thin films.

In this work, we design and fabricate a deep ultraviolet (DUV) light-emitting array consisting of 10 × 10 micro-LEDs (μ-LEDs) with each device having 20 μm in diameter. Strikingly, the array demonstrates a significant enhancement of total light output power by nearly 52% at the injection current of 100 mA, in comparison to a conventional large LED chip whose emitting area is the same as the array. A much higher (~22%) peak external quantum efficiency, as well as a smaller efficiency droop for μ-LED array, was also achieved. The numerical calculation reveals that the performance boost can be attributed to the higher light extraction efficiency at the edge of each μ-LED. Additionally, the far-field pattern measurement shows that the μ-LED array possesses a better forward directionality of emission. These findings shed light on the enhancement of the DUV LEDs performance and provide new insights in controlling the light behavior of the μ-LEDs.

In this work, a hybrid integrated optical transmitter module was designed and fabricated. A proton-exchanged Mach–Zehnder lithium niobate (LiNbO₃) modulator chip was chosen to enhance the output extinction ratio. A fiber was used to adjust the rotation of the polarization direction caused by the optical isolator. The whole optical path structure, including the laser chip, lens, fiber, and modulator chip, was simulated to achieve high optical output efficiency. After a series of process improvements, a module with an output extinction ratio of 34 dB and a bandwidth of 20.5 GHz (from 2 GHz) was obtained. The optical output efficiency of the whole module reached approximately 21%. The link performance of the module was also measured.

A wide wavelength tuning range and single-mode hybrid cavity laser consists of a square Whispering-Gallery (WG) microcavity and a Fabry–Pérot (FP) was introduced and demonstrated. A wavelength tuning range over 12.5 nm from 1760.87 to 1773.39 nm which was single-mode emitting was obtained with the side-mode suppression ratio over 30 dB. The hybrid cavity laser does not need grating etching and special epitaxial structure, which reduces the fabrication difficulty and cost, and shows the potential for gas sensing with absorption lines in this range.

The explosive growth of the global data volume demands new and advanced data storage methods. Here, we report that data storage with ultrahigh capacity (~1 TB per disc) can be realized in low-cost plastics, including polycarbonate (PC), precipitated calcium carbonate (PCC), polystyrene (PS), and polymethyl methacrylate (PMMA), via direct fs laser writing. The focused fs laser can modify the fluorescence of written regions on the surface and in the interior of PMMA, enabling three-dimensional (3D) information storage. Through the 3D laser processing platform, a 50-layer data record with low bit error (0.96%) is archived. Visual reading of data is empowered by the fluorescence contrast. The broad variation of fluorescence intensity assigns 8 gray levels, corresponding to 3 bits on each spot. The gray levels of each layer present high stability after long-term aging cycles, confirming the robustness of data storage. Upon single pulse control via a high-frequency electro-optic modulator (EOM), a fast writing speed (~1 kB/s) is achieved, which is limited by the repetition frequency of the fs laser.

A multi-modal time-to-failure distribution for an electro-migration (EM) structure has been observed and studied from long durationin-situ EM experiment, for which the failure mechanism has been investigated and discussed comprehensively. The mixed EM failure behavior strongly suggest that the fatal voids induced EM failure appear at various locations along the EM structure. This phenomenon is believed to be highly related to the existence of pre-existing voids before EM stress. Meanwhile, the number and location of the pre-existing voids can influence the EM failure mode significantly. Based on our research, a potential direction to improve the EM lifetime of Cu interconnect is presented.

Resistive switching random access memory (RRAM) is considered as one of the potential candidates for next-generation memory. However, obtaining an RRAM device with comprehensively excellent performance, such as high retention and endurance, low variations, as well as CMOS compatibility, etc., is still an open question. In this work, we introduce an insert TaO_x layer into HfO_x-based RRAM to optimize the device performance. Attributing to robust filament formed in the TaO_x layer by a forming operation, the local-field and thermal enhanced effect and interface modulation has been implemented simultaneously. Consequently, the RRAM device features large windows (> 10³), fast switching speed (~ 10 ns), steady retention (> 72 h), high endurance (> 10⁸ cycles), and excellent uniformity of both cycle-to-cycle and device-to-device. These results indicate that inserting the TaO_x layer can significantly improve HfO_x-based device performance, providing a constructive approach for the practical application of RRAM.

We investigated the effect of charge trapping on electrical characteristics of silicon junctionless nanowire transistors which are fabricated on heavily n-type doped silicon-on-insulator substrate. The obvious random telegraph noise and current hysteresis observed at the temperature of 10 K indicate the existence of acceptor-like traps. The position depth of the traps in the oxide from Si/SiO₂ interface is 0.35 nm, calculated by utilizing the dependence of the capture and emission time on the gate voltage. Moreover, by constructing a three-dimensional model of tri-gate device structure in COMSOL Multiphysics simulation software, we achieved the trap density of 1.9 × 10¹² cm^–2 and the energy level position of traps at 0.18 eV below the intrinsic Fermi level.