The absence of large-size gallium nitride (GaN) substrates with low dislocation density remains a primary bottleneck for advancing GaN-based devices. Here, we demonstrate the achievement of 8-inch freestanding GaN substrates grown by hydride vapor phase epitaxy. Critical to this achievement is the improvement in gas-flow uniformity, which ensures exceptional thickness homogeneity and enables the crack-free growth of GaN. After laser lift-off (LLO) separation, the freestanding GaN substrate exhibits superior crystal quality, evidenced by full width at half maximum values of 68 and 54 arcsec for X-ray diffraction rocking curves of (002) and (102) planes, alongside a low dislocation density of 1.6 × 106 cm−2. This approach establishes a robust pathway for the production of large-size GaN substrates, which are essential for advancing next-generation power electronics and high-efficiency photonics.
As one of the core components of IC manufacturing equipment, the electrostatic chuck (ESC) has been widely applied in semiconductor processing such as etching, PVD and CVD. The clamping force of the ESC is one of the most important technical indicators. A multi-physics simulation software COMSOL is used to analyze the factors influencing the clamping force. The curves between the clamping force and the main parameters such as DC voltage, electrode thickness, electrode radius, dielectric thickness and helium gap are obtained. Moreover, the effects of these factors on the clamping force are investigated by means of orthogonal experiments. The results show that the factors can be ranked in order of voltage, electrode radius, helium gap and dielectric thickness according to their importance, which may offer certain reference for the design of ESCs.
The rapid rise in the power conversion efficiency (PCE) of CsPbBr2I-based perovskite solar cells (PSCs), from 4.7% in 2016 to 11.08% in 2020, render it a promising material for use in photovoltaic devices. However, the phase stability and current hysteresis caused by photo-induced phase segregation in CsPbBr2I represent major obstacles to further improvements in the PCE for such devices. In this review, we describe the basic structure and optical properties of CsPbBr2I, and systematically elaborate on the mechanism of the phase transition. We then discuss the strategies in progress to suppress phase transition in CsPbBr2I, and their potential application in the photovoltaic field. Finally, challenges and application prospects for CsPbBr2I PSCs are summarized in the final section of this article.
This paper present a highly-integrated neurostimulator with an on-chip inductive power-recovery frontend and high-voltage stimulus generator. In particular, the power-recovery frontend includes a high-voltage full-wave rectifier (up to 100 V AC input), high-voltage series regulators (24/5 V outputs) and a linear regulator (1.8/3.3 V output) with bandgap voltage reference. With the high voltage output of the series regulator, the proposed neurostimulator could deliver a considerably large current in high electrode-tissue contact impedance. This neurostimulator has been fabricated in a CSMC 1 μm 5/40/700 V BCD process and the total silicon area including pads is 5.8 mm2. Preliminary tests are successful as the neurostimulator shows good stability under a 13.56 MHz AC supply. Compared to previously reported works, our design has advantages of a wide induced voltage range (26-100 V), high output voltage (up to 24 V) and high-level integration, which are suitable for implantable neurostimulators.
The optical properties of polypyrrole (Ppy) thin films upon 2 MeV electron beam irradiation changes with different doses. The induced changes in the optical properties for Ppy thin films were studied in the visible range 300 to 800 nm at room temperature. The optical band gap of the pristine Ppy was found to be 2.19 eV and it decreases up to 1.97 eV for a 50 kGy dose of 2 MeV electron beam. The refractive index dispersion of the samples obeys the single oscillator model. The obtained results suggest that electron beam irradiation changes the optical parameters of Ppy thin films.
This paper presents an image sensor controller that is compatible for depth measurement, which is based on the continuous-wave modulation time-of-flight technology. The image sensor controller is utilized to generate reconfigurable control signals for a 256×256 high speed CMOS image sensor with a conventional image sensing mode and a depth measurement mode. The image sensor controller generates control signals for the pixel array to realize the rolling exposure and the correlated double sampling functions. An refined circuit design technique in the logic level is presented to reduce chip area and power consumption. The chip, with a size of 700×3380 μm2, is fabricated in a standard 0.18 μm CMOS image sensor process. The power consumption estimated by the synthesis tool is 65 mW under a 1.8 V supply voltage and a 100 MHz clock frequency. Our test results show that the image sensor controller functions properly.
The advanced fin-shaped field-effect transistor (FinFET) technology offers higher integration density and stronger channel control capabilities, however, more complex process effects are also introduced which have significant influence on device performance. To address these issues, we complete a design-technology co-optimization (DTCO) focused on FinFET, including both process-induced effect during gate formation and corresponding digital unit optimization design. The 14 nm FinFET complementary metal oxide semiconductor (CMOS) technology is used to illustrate the sensitivity of transistor performance to process-induced effect, specifically the poly pitch effect (PPE) and cut poly effect (CPE). Predictive technology computer aided design (TCAD) simulations have been carried out to evaluate the transistor performance in advance. Based on the results, optimizations in digital unit design is proposed. Fall delay of the digital unit inverter is decreased by 0.7%, and the rise delay is decreased by 2.1%. For multiple selector (MUX2NV), the delay decreases by 4.64% for rise and 3.56% for drop, respectively.
Transistor’s invention revolutionized global society by spawning electronics industry. John Bardeen is among one of the inventors of transistor. He was a genius and one of the most influential semiconductor Physicist of 20th century who won two Nobel prizes in Physics.
Field-effect transistors based on ferroelectrics have attracted intensive interests, because of their non-volatile data retention, rewritability, and non-destructive read-out. In particular, polymeric materials that possess ferroelectric properties are promising for the fabrications of memory devices with high performance, low cost, and large-area manufacturing, by virtue of their good solubility, low-temperature processability, and good chemical stability. In this review, we discuss the material characteristics of ferroelectric polymers, providing an update on the current development of ferroelectric field-effect transistors (Fe-FETs) in non-volatile memory applications.
