GaN/AlGaN high electron mobility transistors (HEMTs) are important devices due to their high-frequency and high-power applications. The two-dimensional (2D) electron density in AlGaN/GaN heterostructures is essential for the design of the state-of-the-art HEMTs. Here, the electro-absorption of GaN/AlGaN HEMTs was investigated using photoluminescence excitation (PLE), which is a sensitive and noncontact optical technique. The built-in electric fields of the GaN and AlGaN layers in HEMTs were derived from the Stark effect in PLE. According to the discontinuity in the displacement electric fields, the 2D electron density in the heterostructures can be estimated from PLE, which agrees with the values obtained from the Hall-effect measurements.

In this work, we demonstrate a low‐thermal‐budget two‐step annealing strategy that integrates microwave annealing (MWA) and supercritical fluid (SCF) treatment to optimize the electrical and structural properties of boron (B)‐implanted Ge substrates. In the first step, MWA enables rapid defect recovery while promoting dopant activation. The subsequent pressure‐controlled CO ₂ treatment further modifies the structural and electrical characteristics of the implanted Ge. Electrical characterization reveals that the most favorable 50 atm treatment reduces the sheet resistance from 49.24 to 25.571 Ω/sq. and increases the Hall mobility from 80.1 to 118 cm ² V ⁻¹ s ⁻¹ compared with MWA‐only treatment. Structural analyses using Raman spectroscopy and transmission electron microscopy indicate improved crystalline quality and reduced implantation‐induced damage under the most favorable investigated treatment condition. This combined MWA–SCF process improves dopant activation and defect recovery under a relatively low additional thermal budget and provides a promising route for advanced Ge‐based device processing.

A force sensing resistor (FSR) consists of printed conducting ink layered on a flexible substrate, with resistance that changes in response to external force, which shown compact, easy to replace, affordable, and suitable for experimental applications. However, the inherent characteristics of FSR architectures present critical challenges, including nonlinear restoring forces, limited durability in harsh environments, and low integration density, which hinder their practical deployment in industrial settings. In this study, remote control of a 3D-printed prosthetic hand based on an FSR integrated with designed circuitry is demonstrated, exhibiting excellent operational stability. The relationship between external force and FSR resistance is monitored within the linear region by a control module that forms a closed circuit using an Arduino microcontroller, the FSR, a battery, and a reference resistor. Additionally, the servomotor is directly driven by the control module, with its angle of rotation dependent on the linearly calibrated FSR signal. Finally, the finger joint synchronizes with the servomotor and FSR signal, utilizing the calibration curve to translate the external force detected by the FSR into a control signal that drives the servomotor to rotate the finger joint structure. These results highlight the significant potential of the FSR integration module for next-generation bionic robotic control and provide a solid foundation for applications in augmented reality and artificial intelligence.

Free-space optical transceiver modules require precise lens assembly to achieve efficient laser-to-fiber coupling. However, optical coupling efficiency is highly sensitive to axial spacing, optical component parameters, and alignment conditions, making conventional parameter tuning time-consuming and inefficient. In this study, a simulation-assisted deep reinforcement learning (DRL) framework is proposed for lens assembly optimization in free-space optical transceiver modules. A dual-lens optical coupling system consisting of a laser diode, a collimating lens, a coupling lens, an optical isolator, and a single-mode fiber was established using a ray-tracing optical simulation environment. A deep deterministic policy gradient agent based on an actor–critic architecture was employed to search the continuous assembly parameter space and maximize the optical coupling efficiency. Under the common benchmark, all five methods produced solutions close to the independent reference efficiency. BO and PSO required the fewest evaluations to reach the 0.95η_REF and 0.99η_REF targets, whereas DDPG showed greater run-to-run variability. To further clarify the influence of reward design on optimization behavior, seven reward-weighting conditions spanning efficiency-only to stability-only formulations were investigated to examine the influence of reward composition on the DDPG optimization behavior. The reward-efficiency analysis indicates that an overemphasis on a single objective may lead to ineffective optimization behavior, whereas the equal-weight condition produced a visually more concentrated coupling-efficiency trajectory in the representative run; however, additional repeated-run and tolerance analyses are required to establish improved stability. These results demonstrate the potential of the proposed simulation-based framework for evaluating optimization strategies in optical design and lens assembly, while further experimental and hardware-level validation is required to assess its applicability to practical optical packaging.

In this study, we report the construction of a high-performance ultraviolet (UV) photodetector (PD) based on a zero-dimensional (0D) graphene quantum dots (GQDs) / two-dimensional (2D) molybdenum disulfide (MoS2) heterojunction. First, the MoS2 crystals were prepared directly on c-plane sapphire substrates by chemical vapor deposition (CVD) technique. Then, Raman spectroscopy and atomic force microscopy (AFM) were conducted to confirm the high quality of the grown MoS2 monolayers. After that, GQDs were synthesized via pulsed laser ablation (PLA) in a cost-effective manner. Compared with the monolayer MoS2-based PD, the GQDs/monolayer MoS2-based PD exhibited 83-fold improvement in responsivity (from 9.9× 102 to 8.5 × 104 A/W) and 106-fold improvement in detectivity (from 3.4 × 1014 to 3.6 × 1016 cm × Hz1/2/W) under UV light illumination. This improved photoresponse is mainly attributed to GQDs induced interfacial charge transfer modulation and trap state engineering, which suppress deep trap mediated persistent photocurrent and facilitate more efficient carrier relaxation. In addition, the monolayer MoS2-based device displayed asymmetric kinetics with a short rise time of 0.54 s and a long fall time of 6.08 s, dominated by deep trap assisted relaxation. After GQDs decoration, the rise time extended to 1.48 s while the fall time decreased to 1.43 s, demonstrating that GQDs could effectively passivate deep traps and reshape the photogating-driven response. These findings show that the GQDs interface engineering presents a viable approach to improving UV photoresponse and tuning carrier dynamics in MoS₂ PD, paving the way for advancing UV sensing and next-generation semiconductor optoelectronic applications.

The increasing demand for high-speed data transmission in artificial intelligence computing and data-center architectures has accelerated the development of compact optical interconnect technologies. In this work, a green InGaN hybrid quantum well-quantum-dot like vertical-cavity surface-emitting laser (hybrid QW-QD-like VCSEL) operating near 510 nm is demonstrated. The device incorporates an InGaN active region and a nanoporous GaN distributed Bragg reflector (NP-DBR) to form a vertical resonant cavity. Optical characterization indicates strong carrier localization behavior and hybrid QW-QD-like recombination in the active region. The fabricated device with a 12 μm aperture exhibits a low threshold current of 1.032 mA (0.9125 kA/cm²) and stable lasing near 510 nm. High-speed modulation measurements show a -3dB bandwidth of 3.18 GHz, and data transmission experiments achieve a bit-error rate of 2.6 × 10⁻³ at 4.5 Gb/s, below the forward-error-correction limit. These results demonstrate the potential of green InGaN hybrid QW-QD like VCSELs for visible-light communication (VLC) and short reach optical interconnect applications.